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Instructional theory

An instructional theory is "a theory that offers explicit guidance on how to better help people learn and develop." It provides insights about what is likely to happen and why with respect to different kinds of teaching and learning activities while helping indicate approaches for their evaluation. Instructional designers focus on how to best structure material and instructional behavior to facilitate learning.

Development
Originating in the United States in the late 1970s, instructional theory is influenced by three basic theories in educational thought: behaviorism, the theory that helps us understand how people conform to predetermined standards; cognitivism, the theory that learning occurs through mental associations; and constructivism, the theory explores the value of human activity as a critical function of gaining knowledge. Instructional theory is heavily influenced by the 1956 work of Benjamin Bloom, a University of Chicago professor, and the results of his Taxonomy of Education Objectives—one of the first modern codifications of the learning process. One of the first instructional theorists was Robert M. Gagne, who in 1965 published Conditions of Learning for the Florida State University's Department of Educational Research.

Definition
Instructional theory is different than learning theory. A learning theory describes how learning takes place, and an instructional theory prescribes how to better help people learn. Learning theories often inform instructional theory, and three general theoretical stances take part in this influence: behaviorism (learning as response acquisition), cognitivism (learning as knowledge acquisition), and constructivism (learning as knowledge construction). Instructional theory helps us create conditions that increases the probability of learning. Its goal is understanding the instructional system and to improve the process of instruction.

Overview
Instructional theories identify what instruction or teaching should be like. It outlines strategies that an educator may adopt to achieve the learning objectives. Instructional theories are adapted based on the educational content and more importantly the learning style of the students. They are used as teaching guidelines/tools by teachers/trainers to facilitate learning. Instructional theories encompass different instructional methods, models and strategies.

David Merrill's First Principles of Instruction discusses universal methods of instruction, situational methods and core ideas of the post-industrial paradigm of instruction.

Universal Methods of Instruction:

Situational Methods:
 * Task-Centered Principle - instruction should use a progression of increasingly complex whole tasks.
 * Demonstration Principle - instruction should guide learners through a skill and engage peer discussion/demonstration.
 * Application Principle - instruction should provide intrinsic or corrective feedback and engage peer-collaboration.
 * Activation Principle - instruction should build upon prior knowledge and encourage learners to acquire a structure for organizing new knowledge.
 * Integration Principle - instruction should engage learners in peer-critiques and synthesizing newly acquired knowledge.

based on different approaches to instruction based on different learning outcomes: Core ideas for the Post-industrial Paradigm of Instruction: Four tasks of Instructional theory:
 * Role play
 * Synectics
 * Mastery learning
 * Direct instruction
 * Discussion
 * Conflict resolution
 * Peer learning
 * Experiential learning
 * Problem-based learning
 * Simulation-based learning
 * Knowledge
 * Comprehension
 * Application
 * Analysis
 * Synthesis
 * Evaluation
 * Affective development
 * Integrated learning
 * Learner centered vs. teacher centered instruction – with respect to the focus, instruction can be based on the capability and style of the learner or the teacher.
 * Learning by doing vs. teacher presenting – Students often learn more by doing rather than simply listening to instructions given by the teacher.
 * Attainment based vs. time based progress – The instruction can either be based on the focus on the mastery of the concept or the time spent on learning the concept.
 * Customized vs. standardized instruction – The instruction can be different for different learners or the instruction can be given in general to the entire classroom
 * Criterion referenced vs. norm referenced instruction – Instruction related to different types of evaluations.
 * Collaborative vs. individual instruction – Instruction can be for a team of students or individual students.
 * Enjoyable vs. unpleasant instructions – Instructions can create a pleasant learning experience or a negative one (often to enforce discipline). Teachers must take care to ensure positive experiences.
 * Knowledge selection
 * Knowledge sequence
 * Interaction management
 * Setting of interaction environment

Critiques
Paulo Freire's work appears to critique instructional approaches that adhere to the knowledge acquisition stance, and his work Pedagogy of the Oppressed has had a broad influence over a generation of American educators with his critique of various "banking" models of education and analysis of the teacher-student relationship.

Freire explains, "Narration (with the teacher as narrator) leads the students to memorize mechanically the narrated content. Worse yet, it turns them into "containers", into "receptacles" to be "filled" by the teacher. The more completely she fills the receptacles, the better a teacher she is. The more meekly the receptacles permit themselves to be filled, the better students they are." In this way he explains educator creates an act of depositing knowledge in a student. The student thus becomes a repository of knowledge. Freire explains that this system that diminishes creativity and knowledge suffers. Knowledge, according to Freire, comes about only through the learner by inquiry and pursuing the subjects in the world and through interpersonal interaction.

Freire further states, "In the banking concept of education, knowledge is a gift bestowed by those who consider themselves knowledgeable upon those whom they consider to know nothing. Projecting an absolute ignorance onto others, a characteristic of the ideology of oppression, negates education and knowledge as processes of inquiry. The teacher presents himself to his students as their necessary opposite; by considering their ignorance absolute, he justifies his own existence. The students, alienated like the slave in the Hegelian dialectic, accept their ignorance as justifying the teacher's existence—but, unlike the slave, they never discover that they educate the teacher." Freire then offered an alternative stance and wrote, "The raison d'etre of libertarian education, on the other hand, lies in its drive towards reconciliation. Education must begin with the solution of the teacher-student contradiction, by reconciling the poles of the contradiction so that both are simultaneously teachers and students."

In the article, "A process for the critical analysis of instructional theory", the authors use an ontology-building process to review and analyze concepts across different instructional theories. Here are their findings:
 * Concepts exist in theoretical writing that theorists do not address directly.
 * These tacit concepts, which supply the ontological categories, enable a more detailed comparison of theories beyond specific terminologies.
 * Divergences between theories can be concealed behind common terms used by different theorists.
 * A false sense of understanding often arises from a cursory, uncritical reading of the theories.
 * Discontinuities and gaps are revealed within the theoretical literature when the tacit concepts are elicited.

title: Instructional theory


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Talk:Ira

Make this a disambiguation page?
Should the kind of IRA (Individual Retirement Account) that is financial in nature have a place on the IRA page? --Dante Alighieri 19:40 21 May 2003 (UTC)

 * Ideally this should be a disambiguation page. But we need to orphan this page first in order to prevent misdirected linking (most pages linking here intend to go to an article about the Irish Republican Army. --mav

 * Surely the Irish Republican Army meaning is vastly the more significant of the two. Renaming the page because of a purely US financial TLA would be silly. Tannin

 * I don't think so. IRA's are very common in the states so there is a reasonable ambiguity problem here that should be resolved. --mav

 * And there are similar ones here in Australia - one in particular that I notice every time I see it here on Wikipedia but has sliped my colander of a mind at the moment. (This is Monday, right?) If I changed those to disambiguation pages, there would be a serious outcry, and rightly so. Why should a wordwide meaning give way to a purely local (and undoubtedly temporary) one?

 * This isn't something that is going to be resolved by discussion though: the facts are plain, and there is no particular rational argument to be made one way or another that isn't obvious at first glance. It's simply a judgement call. I firmly oppose the change. If others from the international Wikipedia community agree with me, then it should not be changed. If, on the other hand, a "consensus minus one" situation develops, then (and only then) the change should go ahead. Let's see what the general opinion is. Tannin

 * This isn't a policy or anything so I don't see a point in having to wait for a "consensus" to emerge. But since you mentioned it, Dante did ask the mailing list about this exact issue and the consensus so far there is that this should be a disambiguation page. The usage in the USA is not going to go away anytime soon - besides there aren't that many pages linking here as it is (unlike with football). Just about any acronym that is less than four characters long is going to be ambiguous. Heck, if there weren't so many damn links to USA I would advocate that that too be made a disambiguation page (there is a United Software Association and probably many other uses of USA). In short we shouldn't supporting lazy linking behavior for short acronyms since these are used by many different entities. It would also be interesting to know all the different uses for these ambiguously short acronyms. --mav 06:55 22 May 2003 (UTC)

I wouldn't like to see IRA become a disambiguation page, but I was staggered to find that the first hit when putting IRA into google is the International Reading Association! So I concede that there is an argument for doing so. Mintguy

Make this a redirect page?
You could make IRA a redirect page, then at the top of the page that it goes to, say "IRA redirects here. For other uses, see IRA (disambiguation)". I've seen this format used on Wikipedia elsewhere. Evercat 19:37 23 May 2003 (UTC)

If this is indeed a disambig page
then according to the Manual of Style, there shouldn't be any links on it except to the articles it is disambiguating. Am I right? Palmiro | Talk 16:10, 13 November 2005 (UTC)
 * Absolutely! I removed them last week but they crept back in. It's fixed now.--Commander Keane 16:44, 13 November 2005 (UTC)

insightful
luved it I'll keep reading deep Haughtingghost (talk) 12:51, 20 September 2021 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Ira


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Infusoria

Infusoria is a word used to describe various freshwater microorganisms, including ciliates, copepods, euglenoids, planktonic crustaceans, protozoa, unicellular algae and small invertebrates. Some authors (e.g., Bütschli) have used the term as a synonym for Ciliophora. In modern, formal classifications, the term is considered obsolete; the microorganisms previously and colloquially referred to as Infusoria are mostly assigned to the kingdom Protista.

In other contexts, the term is used to define various aquatic microorganisms found in decomposing matter.

Aquarium use
Certain microorganisms, including cyclops and daphnia (among others), are sold as a supplemental fish food. Some fish stores or pet shops may have these infusoria available for live purchase, but typically they are sold in frozen cubes—for example, by the Japan-based fish food brand Hikari. Still, some advanced aquarists, with especially large collections of fish, will breed and cultivate their own supplies of the microorganisms.

Infusoria are especially used by aquarists and fish breeders to feed fish fry; because of their small sizes, infusoria can be used to rear newly-hatched offspring of many common (and also less common) aquarium species. Many average home aquaria are unable to naturally supply sufficient infusoria for fish-rearing, so hobbyists may create and maintain their own cultures, either through utilizing their own existing aquarium water or by using one of the many commercial cultures available.

Infusoria can be cultured at-home by soaking any decomposing vegetative matter, such as papaya or cucumber peels, in a jar of aged (i.e., chlorine-free) water, preferably from an existing aquarium setup. The culture starts to proliferate in two to three days, depending on temperature and light received. The water first turns cloudy because of a rise in levels of bacteria, but clears up once the infusoria consume them. At this point, the infusoria are usually visible to the naked eye as small, white motile specks. They can be easily fed to fish with the use of a large turkey-baster or by gently scooping with a very fine net. Additionally, the water in which the infusoria are kept in can be changed periodically, even one to two times per week, by draining and replacing up to 50% of the volume of water (for hygienic and maintenance purposes).

title: Infusoria


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ISO/IEC 8859-1

ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. ISO/IEC 8859-1 encodes what it refers to as "Latin alphabet no. 1", consisting of 191 characters from the Latin script. This character-encoding scheme is used throughout the Americas, Western Europe, Oceania, and much of Africa. It is the basis for some popular 8-bit character sets and the first two blocks of characters in Unicode.

ISO-8859-1 was (according to the standard, at least) the default encoding of documents delivered via HTTP with a MIME type beginning with text/. , 1.2% of all web sites use ISO/IEC 8859-1. It is the most declared single-byte character encoding, but as Web browsers and the HTML5 standard interpret them as the superset Windows-1252, these documents may include characters from that set.

Depending on the country or language, use (on websites at least) can be much higher than the global average, e.g. (including Windows-1252), for Brazil according to website use, use is at 3.4%, and in Germany at  2.7%.

ISO-8859-1 was the default encoding of the values of certain descriptive HTTP headers, and defined the repertoire of characters allowed in HTML 3.2 documents, and is specified by many other standards. It's rarely assumed to be the encoding of text in operating systems (while it was very common in the past), though if an 8-bit encoding is used then its superset encoding Windows-1252 is most likely to be used, on Microsoft Windows if there is no byte order mark (BOM); this is only gradually being changed to UTF-8.

ISO-8859-1 is the IANA preferred name for this standard when supplemented with the C0 and C1 control codes from ISO/IEC 6429. The following other aliases are registered: iso-ir-100, csISOLatin1, latin1, l1, IBM819. Code page 28591 a.k.a. Windows-28591 is used for it in Windows. IBM calls it code page 819 or CP819 (CCSID 819). Oracle calls it WE8ISO8859P1.

Coverage
Each character is encoded as a single eight-bit code value. These code values can be used in almost any data interchange system to communicate in the following languages (while it may exclude correct quotation marks such as for many languages including German and Icelandic):

Modern languages with complete coverage
• Afrikaans

• Albanian

• Basque

• Breton

• Corsican

• English

• Faroese

• Galician

• Icelandic

• Ido

• Irish

• Indonesian

• Italian

• Leonese

• Lojban

• Luxembourgish

• Malay

• Manx

• Norwegian

• Occitan

• Portuguese

• Rhaeto-Romanic

• Rotokas

• Scottish Gaelic

• Scots

• Southern Sami

• Spanish

• Swahili

• Swedish

• Tagalog

• Toki Pona

• Walloon

 * Notes

Languages with incomplete coverage
ISO-8859-1 was commonly used for certain languages, even though it lacks characters used by these languages. In most cases, only a few letters are missing or they are rarely used, and they can be replaced with characters that are in ISO-8859-1 using some form of typographic approximation. The following table lists such languages.

The letter ÿ, which appears in French only very rarely, mainly in city names such as L'Haÿ-les-Roses and never at the beginning of words, is included only in lowercase form. The slot corresponding to its uppercase form is occupied by the lowercase letter ß from the German language, which did not have an uppercase form at the time when the standard was created.

Quotation marks
For some languages listed above, the correct typographical quotation marks are missing, as only « », " ", and ' ' are included. Also, this scheme does not provide for oriented (6- or 9-shaped) single or double quotation marks. Some fonts will display the spacing grave accent (0x60) and the apostrophe (0x27) as a matching pair of oriented single quotation marks (see ), but this is not considered part of the modern standard.

History
ISO 8859-1 was based on the Multinational Character Set (MCS) used by Digital Equipment Corporation (DEC) in the popular VT220 terminal in 1983. It was developed within the European Computer Manufacturers Association (ECMA), and published in March 1985 as ECMA-94, by which name it is still sometimes known. The second edition of ECMA-94 (June 1986) also included ISO 8859-2, ISO 8859-3, and ISO 8859-4 as part of the specification.

The original draft of ISO 8859-1 placed French Œ and œ at code points 215 (0xD7) and 247 (0xF7), as in the MCS. However, the delegate from France, being neither a linguist nor a typographer, falsely stated that these are not independent French letters on their own, but mere ligatures (like ﬁ or ﬂ), supported by the delegate team from Bull Publishing Company, who regularly did not print French with Œ/œ in their house style at the time. An anglophone delegate from Canada insisted on retaining Œ/œ but was rebuffed by the French delegate and the team from Bull. These code points were soon filled with × and ÷ under the suggestion of the German delegation. Support for French was further reduced when it was again falsely stated that the letter ÿ is "not French", resulting in the absence of the capital Ÿ. In fact, the letter ÿ is found in a number of French proper names, and the capital letter has been used in dictionaries and encyclopedias. These characters were added to ISO/IEC 8859-15:1999. BraSCII matches the original draft.

In 1985, Commodore adopted ECMA-94 for its new AmigaOS operating system. The Seikosha MP-1300AI impact dot-matrix printer, used with the Amiga 1000, included this encoding.

In 1990, the first version of Unicode used the code points of ISO-8859-1 as the first 256 Unicode code points.

In 1992, the IANA registered the character map ISO_8859-1:1987, more commonly known by its preferred MIME name of ISO-8859-1 (note the extra hyphen over ISO 8859-1), a superset of ISO 8859-1, for use on the Internet. This map assigns the C0 and C1 control codes to the unassigned code values thus provides for 256 characters via every possible 8-bit value.

ISO/IEC 8859-15
ISO/IEC 8859-15 was developed in 1999, as an update of ISO/IEC 8859-1. It provides some characters for French and Finnish text and the euro sign, which are missing from ISO/IEC 8859-1. This required the removal of some infrequently used characters from ISO/IEC 8859-1, including fraction symbols and letter-free diacritics: ¤, ¦, ¨, ´, ¸, ¼, ½, and ¾. Ironically, three of the newly added characters (Œ, œ, and Ÿ) had already been present in DEC's 1983 Multinational Character Set (MCS), the predecessor to ISO/IEC 8859-1 (1987). Since their original code points were now reused for other purposes, the characters had to be reintroduced under different, less logical code points.

ISO-IR-204, a more minor modification (called code page 61235 by FreeDOS), had been registered in 1998, altering ISO-8859-1 by replacing the universal currency sign (¤) with the euro sign (the same substitution made by ISO-8859-15).

Windows-1252
The popular Windows-1252 character set adds all the missing characters provided by ISO/IEC 8859-15, plus a number of typographic symbols, by replacing the rarely used C1 controls in the range 128 to 159 (hex 80 to 9F). It is very common to mislabel Windows-1252 text as being in ISO-8859-1. A common result was that all the quotes and apostrophes (produced by "smart quotes" in word-processing software) were replaced with question marks or boxes on non-Windows operating systems, making text difficult to read. Many Web browsers and e-mail clients will interpret ISO-8859-1 control codes as Windows-1252 characters, and that behavior was later standardized in HTML5.

Mac Roman
The Apple Macintosh computer introduced a character encoding called Mac Roman in 1984. It was meant to be suitable for Western European desktop publishing. It is a superset of ASCII, and has most of the characters that are in ISO-8859-1 and all the extra characters from Windows-1252, but in a totally different arrangement. The few printable characters that are in ISO/IEC 8859-1, but not in this set, are often a source of trouble when editing text on Web sites using older Macintosh browsers, including the last version of Internet Explorer for Mac.

Other
DOS has code page 850, which has all printable characters that ISO-8859-1 has, albeit in a totally different arrangement, plus the most widely used graphic characters from code page 437.

Between 1989 and 2015, Hewlett-Packard used another superset of ISO-8859-1 on many of their calculators. This proprietary character set was sometimes referred to simply as "ECMA-94" as well. HP also has code page 1053, which adds the medium shade (▒, U+2592) at 0x7F.

Several EBCDIC code pages were purposely designed to have the same set of characters as ISO-8859-1, to allow easy conversion between them.

title: ISO/IEC 8859-1


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ISO/IEC 8859

ISO/IEC 8859 is a joint ISO and IEC series of standards for 8-bit character encodings. The series of standards consists of numbered parts, such as ISO/IEC 8859-1, ISO/IEC 8859-2, etc. There are 15 parts, excluding the abandoned ISO/IEC 8859-12. The ISO working group maintaining this series of standards has been disbanded.

ISO/IEC 8859 parts 1, 2, 3, and 4 were originally Ecma International standard ECMA-94.

Introduction
While the bit patterns of the 95 printable ASCII characters are sufficient to exchange information in modern English, most other languages that use Latin alphabets need additional symbols not covered by ASCII. ISO/IEC 8859 sought to remedy this problem by utilizing the eighth bit in an 8-bit byte to allow positions for another 96 printable characters. Early encodings were limited to 7 bits because of restrictions of some data transmission protocols, and partially for historical reasons. However, more characters were needed than could fit in a single 8-bit character encoding, so several mappings were developed, including at least ten suitable for various Latin alphabets.

The ISO/IEC 8859 standard parts only define printable characters, although they explicitly set apart the byte ranges 0x00–1F and 0x7F–9F as "combinations that do not represent graphic characters" (i.e. which are reserved for use as control characters) in accordance with ISO/IEC 4873; they were designed to be used in conjunction with a separate standard defining the control functions associated with these bytes, such as ISO 6429 or ISO 6630. To this end a series of encodings registered with the IANA add the C0 control set (control characters mapped to bytes 0 to 31) from ISO 646 and the C1 control set (control characters mapped to bytes 128 to 159) from ISO 6429, resulting in full 8-bit character maps with most, if not all, bytes assigned. These sets have ISO-8859-n as their preferred MIME name or, in cases where a preferred MIME name is not specified, their canonical name. Many people use the terms ISO/IEC 8859-n and ISO-8859-n interchangeably. ISO/IEC 8859-11 did not get such a charset assigned, presumably because it was almost identical to TIS 620.

Characters
The ISO/IEC 8859 standard is designed for reliable information exchange, not typography; the standard omits symbols needed for high-quality typography, such as optional ligatures, curly quotation marks, dashes, etc. As a result, high-quality typesetting systems often use proprietary or idiosyncratic extensions on top of the ASCII and ISO/IEC 8859 standards, or use Unicode instead.

An inexact rule based on practical experience states that if a character or symbol was not already part of a widely used data-processing character set and was also not usually provided on typewriter keyboards for a national language, it did not get in. Hence the directional double quotation marks « and » used for some European languages were included, but not the directional double quotation marks “ and ” used for English and some other languages.

French did not get its œ and Œ ligatures because they could be typed as 'oe'. Likewise, Ÿ, needed for all-caps text, was dropped as well. Albeit under different codepoints, these three characters were later reintroduced with ISO/IEC 8859-15 in 1999, which also introduced the new euro sign character €. Likewise Dutch did not get the ĳ and Ĳ letters, because Dutch speakers had become used to typing these as two letters instead.

Romanian did not initially get its Ș/ș and Ț/ț (with comma) letters, because these letters were initially unified with Ş/ş and Ţ/ţ (with cedilla) by the Unicode Consortium, considering the shapes with comma beneath to be glyph variants of the shapes with cedilla. However, the letters with explicit comma below were later added to the Unicode standard and are also in ISO/IEC 8859-16.

Most of the ISO/IEC 8859 encodings provide diacritic marks required for various European languages using the Latin script. Others provide non-Latin alphabets: Greek, Cyrillic, Hebrew, Arabic and Thai. Most of the encodings contain only spacing characters, although the Thai, Hebrew, and Arabic ones do also contain combining characters.

The standard makes no provision for the scripts of East Asian languages (CJK), as their ideographic writing systems require many thousands of code points. Although it uses Latin based characters, Vietnamese does not fit into 96 positions (without using combining diacritics such as in Windows-1258) either. Each Japanese syllabic alphabet (hiragana or katakana, see Kana) would fit, as in JIS X 0201, but like several other alphabets of the world they are not encoded in the ISO/IEC 8859 system.

The parts of ISO/IEC 8859
ISO/IEC 8859 is divided into the following parts:

Each part of ISO/IEC 8859 is designed to support languages that often borrow from each other, so the characters needed by each language are usually accommodated by a single part. However, there are some characters and language combinations that are not accommodated without transcriptions. Efforts were made to make conversions as smooth as possible. For example, German has all of its seven special characters at the same positions in all Latin variants (1–4, 9, 10, 13–16), and in many positions the characters only differ in the diacritics between the sets. In particular, variants 1–4 were designed jointly, and have the property that every encoded character appears either at a given position or not at all.

Table
unassigned code points. new additions in ISO/IEC 8859-7:2003 and ISO/IEC 8859-8:1999 versions, previously unassigned.

Relationship to Unicode and the UCS
Since 1991, the Unicode Consortium has been working with ISO and IEC to develop the Unicode Standard and ISO/IEC 10646: the Universal Character Set (UCS) in tandem. Newer editions of ISO/IEC 8859 express characters in terms of their Unicode/UCS names and the U+nnnn notation, effectively causing each part of ISO/IEC 8859 to be a Unicode/UCS character encoding scheme that maps a very small subset of the UCS to single 8-bit bytes. The first 256 characters in Unicode and the UCS are identical to those in ISO/IEC-8859-1 (Latin-1).

Single-byte character sets including the parts of ISO/IEC 8859 and derivatives of them were favoured throughout the 1990s, having the advantages of being well-established and more easily implemented in software: the equation of one byte to one character is simple and adequate for most single-language applications, and there are no combining characters or variant forms. As Unicode-enabled operating systems became more widespread, ISO/IEC 8859 and other legacy encodings became less popular. While remnants of ISO 8859 and single-byte character models remain entrenched in many operating systems, programming languages, data storage systems, networking applications, display hardware, and end-user application software, most modern computing applications use Unicode internally, and rely on conversion tables to map to and from other encodings, when necessary.

Current status
The ISO/IEC 8859 standard was maintained by ISO/IEC Joint Technical Committee 1, Subcommittee 2, Working Group 3 (ISO/IEC JTC 1/SC 2/WG 3). In June 2004, WG 3 disbanded, and maintenance duties were transferred to SC 2. The standard is not currently being updated, as the Subcommittee's only remaining working group, WG 2, is concentrating on development of Unicode's Universal Coded Character Set.

The WHATWG Encoding Standard, which specifies the character encodings permitted in HTML5 which compliant browsers must support, includes most parts of ISO/IEC 8859, except for parts 1, 9 and 11, which are instead interpreted as Windows-1252, Windows-1254 and Windows-874 respectively. Authors of new pages and the designers of new protocols are instructed to use UTF-8 instead.

title: ISO/IEC 8859


text:
Infrared

Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with waves that are just longer than those of red light (the longest waves in the visible spectrum), so IR is invisible to the human eye. IR is generally understood to include wavelengths from around 750 nm to 1 mm. IR is commonly divided between longer-wavelength thermal IR, emitted from terrestrial sources, and shorter-wavelength IR or near-IR, part of the solar spectrum. Longer IR wavelengths (30–100 μm) are sometimes included as part of the terahertz radiation band. Almost all black-body radiation from objects near room temperature is in the IR band. As a form of electromagnetic radiation, IR carries energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon.

It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered that infrared radiation is a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. Slightly more than half of the energy from the Sun was eventually found, through Herschel's studies, to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an important effect on Earth's climate.

Infrared radiation is emitted or absorbed by molecules when changing rotational-vibrational movements. It excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range.

Infrared radiation is used in industrial, scientific, military, commercial, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space such as molecular clouds, to detect objects such as planets, and to view highly red-shifted objects from the early days of the universe. Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, to assist firefighting, and to detect the overheating of electrical components. Military and civilian applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm. Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops, remote temperature sensing, short-range wireless communication, spectroscopy, and weather forecasting.

Definition and relationship to the electromagnetic spectrum
There is no universally accepted definition of the range of infrared radiation. Typically, it is taken to extend from the nominal red edge of the visible spectrum at 700 nm to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz. Beyond infrared is the microwave portion of the electromagnetic spectrum. Increasingly, terahertz radiation is counted as part of the microwave band, not infrared, moving the band edge of infrared to 0.1 mm (3 THz).

Nature
Sunlight, at an effective temperature of 5,780 K (5,510 °C, 9,940 °F), is composed of near-thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kW per square meter at sea level. Of this energy, 527 W is infrared radiation, 445 W is visible light, and 32 W is ultraviolet radiation. Nearly all the infrared radiation in sunlight is near infrared, shorter than 4 μm.

On the surface of Earth, at far lower temperatures than the surface of the Sun, some thermal radiation consists of infrared in the mid-infrared region, much longer than in sunlight. Black-body, or thermal, radiation is continuous: it radiates at all wavelengths. Of these natural thermal radiation processes, only lightning and natural fires are hot enough to produce much visible energy, and fires produce far more infrared than visible-light energy.

Regions
In general, objects emit infrared radiation across a spectrum of wavelengths, but sometimes only a limited region of the spectrum is of interest because sensors usually collect radiation only within a specific bandwidth. Thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wien's displacement law. The infrared band is often subdivided into smaller sections, although how the IR spectrum is thereby divided varies between different areas in which IR is employed.

Visible limit
Infrared radiation is generally considered to begin with wavelengths longer than visible by the human eye. There is no hard wavelength limit to what is visible, as the eye's sensitivity decreases rapidly but smoothly, for wavelengths exceeding about 700 nm. Therefore wavelengths just longer than that can be seen if they are sufficiently bright, though they may still be classified as infrared according to usual definitions. Light from a near-IR laser may thus appear dim red and can present a hazard since it may actually be quite bright. And even IR at wavelengths up to 1,050 nm from pulsed lasers can be seen by humans under certain conditions.

Commonly used subdivision scheme
A commonly used subdivision scheme is:

NIR and SWIR together is sometimes called "reflected infrared", whereas MWIR and LWIR is sometimes referred to as "thermal infrared".

CIE division scheme
The International Commission on Illumination (CIE) recommended the division of infrared radiation into the following three bands:

ISO 20473 scheme
ISO 20473 specifies the following scheme:

Astronomy division scheme
Astronomers typically divide the infrared spectrum as follows:

These divisions are not precise and can vary depending on the publication. The three regions are used for observation of different temperature ranges, and hence different environments in space.

The most common photometric system used in astronomy allocates capital letters to different spectral regions according to filters used; I, J, H, and K cover the near-infrared wavelengths; L, M, N, and Q refer to the mid-infrared region. These letters are commonly understood in reference to atmospheric windows and appear, for instance, in the titles of many papers.

Sensor response division scheme

A third scheme divides up the band based on the response of various detectors:
 * Near-infrared: from 0.7 to 1.0 μm (from the approximate end of the response of the human eye to that of silicon).
 * Short-wave infrared: 1.0 to 3 μm (from the cut-off of silicon to that of the MWIR atmospheric window). InGaAs covers to about 1.8 μm; the less sensitive lead salts cover this region. Cryogenically cooled MCT detectors can cover the region of 1.0–2.5μm.
 * Mid-wave infrared: 3 to 5 μm (defined by the atmospheric window and covered by indium antimonide, InSb and mercury cadmium telluride, HgCdTe, and partially by lead selenide, PbSe).
 * Long-wave infrared: 8 to 12, or 7 to 14 μm (this is the atmospheric window covered by HgCdTe and microbolometers).
 * Very-long wave infrared (VLWIR) (12 to about 30 μm, covered by doped silicon).

Near-infrared is the region closest in wavelength to the radiation detectable by the human eye. mid- and far-infrared are progressively further from the visible spectrum. Other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (the common silicon detectors are sensitive to about 1,050 nm, while InGaAs's sensitivity starts around 950 nm and ends between 1,700 and 2,600 nm, depending on the specific configuration). No international standards for these specifications are currently available.

The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. Particularly intense near-IR light (e.g., from lasers, LEDs or bright daylight with the visible light filtered out) can be detected up to approximately 780 nm, and will be perceived as red light. Intense light sources providing wavelengths as long as 1,050 nm can be seen as a dull red glow, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and the eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the Wood effect that consists of IR-glowing foliage.

Telecommunication bands
In optical communications, the part of the infrared spectrum that is used is divided into seven bands based on availability of light sources, transmitting/absorbing materials (fibers), and detectors:

The C-band is the dominant band for long-distance telecommunication networks. The S and L bands are based on less well established technology, and are not as widely deployed.

Heat

Infrared radiation is popularly known as "heat radiation", but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Objects at room temperature will emit radiation concentrated mostly in the 8 to 25 μm band, but this is not distinct from the emission of visible light by incandescent objects and ultraviolet by even hotter objects (see black body and Wien's displacement law).

Heat is energy in transit that flows due to a temperature difference. Unlike heat transmitted by thermal conduction or thermal convection, thermal radiation can propagate through a vacuum. Thermal radiation is characterized by a particular spectrum of many wavelengths that are associated with emission from an object, due to the vibration of its molecules at a given temperature. Thermal radiation can be emitted from objects at any wavelength, and at very high temperatures such radiation is associated with spectra far above the infrared, extending into visible, ultraviolet, and even X-ray regions (e.g. the solar corona). Thus, the popular association of infrared radiation with thermal radiation is only a coincidence based on typical (comparatively low) temperatures often found near the surface of planet Earth.

The concept of emissivity is important in understanding the infrared emissions of objects. This is a property of a surface that describes how its thermal emissions deviate from the ideal of a black body. To further explain, two objects at the same physical temperature may not show the same infrared image if they have differing emissivity. For example, for any pre-set emissivity value, objects with higher emissivity will appear hotter, and those with a lower emissivity will appear cooler (assuming, as is often the case, that the surrounding environment is cooler than the objects being viewed). When an object has less than perfect emissivity, it obtains properties of reflectivity and/or transparency, and so the temperature of the surrounding environment is partially reflected by and/or transmitted through the object. If the object were in a hotter environment, then a lower emissivity object at the same temperature would likely appear to be hotter than a more emissive one. For that reason, incorrect selection of emissivity and not accounting for environmental temperatures will give inaccurate results when using infrared cameras and pyrometers.

Night vision
Infrared is used in night vision equipment when there is insufficient visible light to see. Night vision devices operate through a process involving the conversion of ambient light photons into electrons that are then amplified by a chemical and electrical process and then converted back into visible light. Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source.

The use of infrared light and night vision devices should not be confused with thermal imaging, which creates images based on differences in surface temperature by detecting infrared radiation (heat) that emanates from objects and their surrounding environment.

Thermography
Infrared radiation can be used to remotely determine the temperature of objects (if the emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry. Thermography (thermal imaging) is mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to greatly reduced production costs.

Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nm or 9–14 μm) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their temperatures, according to the black-body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence the name).

Hyperspectral imaging

A hyperspectral image is a "picture" containing continuous spectrum through a wide spectral range at each pixel. Hyperspectral imaging is gaining importance in the field of applied spectroscopy particularly with NIR, SWIR, MWIR, and LWIR spectral regions. Typical applications include biological, mineralogical, defence, and industrial measurements.

Thermal infrared hyperspectral imaging can be similarly performed using a thermographic camera, with the fundamental difference that each pixel contains a full LWIR spectrum. Consequently, chemical identification of the object can be performed without a need for an external light source such as the Sun or the Moon. Such cameras are typically applied for geological measurements, outdoor surveillance and UAV applications.

Other imaging
In infrared photography, infrared filters are used to capture the near-infrared spectrum. Digital cameras often use infrared blockers. Cheaper digital cameras and camera phones have less effective filters and can view intense near-infrared, appearing as a bright purple-white color. This is especially pronounced when taking pictures of subjects near IR-bright areas (such as near a lamp), where the resulting infrared interference can wash out the image. There is also a technique called 'T-ray' imaging, which is imaging using far-infrared or terahertz radiation. Lack of bright sources can make terahertz photography more challenging than most other infrared imaging techniques. Recently T-ray imaging has been of considerable interest due to a number of new developments such as terahertz time-domain spectroscopy.

Tracking
Infrared tracking, also known as infrared homing, refers to a passive missile guidance system, which uses the emission from a target of electromagnetic radiation in the infrared part of the spectrum to track it. Missiles that use infrared seeking are often referred to as "heat-seekers" since infrared (IR) is just below the visible spectrum of light in frequency and is radiated strongly by hot bodies. Many objects such as people, vehicle engines, and aircraft generate and retain heat, and as such, are especially visible in the infrared wavelengths of light compared to objects in the background.

Heating
Infrared radiation can be used as a deliberate heating source. For example, it is used in infrared saunas to heat the occupants. It may also be used in other heating applications, such as to remove ice from the wings of aircraft (de-icing). Infrared radiation is used in cooking, known as broiling or grilling. One energy advantage is that the IR energy heats only opaque objects, such as food, rather than the air around them.

Infrared heating is also becoming more popular in industrial manufacturing processes, e.g. curing of coatings, forming of plastics, annealing, plastic welding, and print drying. In these applications, infrared heaters replace convection ovens and contact heating.

Cooling
A variety of technologies or proposed technologies take advantage of infrared emissions to cool buildings or other systems. The LWIR (8–15 μm) region is especially useful since some radiation at these wavelengths can escape into space through the atmosphere's infrared window. This is how passive daytime radiative cooling (PDRC) surfaces are able to achieve sub-ambient cooling temperatures under direct solar intensity, enhancing terrestrial heat flow to outer space with zero energy consumption or pollution. PDRC surfaces minimize shortwave solar reflectance to lessen heat gain while maintaining strong longwave infrared (LWIR) thermal radiation heat transfer. When imagined on a worldwide scale, this cooling method has been proposed as a way to slow and even reverse global warming, with some estimates proposing a global surface area coverage of 1-2% to balance global heat fluxes.

Communications
IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants. These devices usually conform to standards published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation that may be concentrated by a lens into a beam that the user aims at the detector. The beam is modulated, i.e. switched on and off, according to a code which the receiver interprets. Usually very near-IR is used (below 800 nm) for practical reasons. This wavelength is efficiently detected by inexpensive silicon photodiodes, which the receiver uses to convert the detected radiation to an electric current. That electrical signal is passed through a high-pass filter which retains the rapid pulsations due to the IR transmitter but filters out slowly changing infrared radiation from ambient light. Infrared communications are useful for indoor use in areas of high population density. IR does not penetrate walls and so does not interfere with other devices in adjoining rooms. Infrared is the most common way for remote controls to command appliances. Infrared remote control protocols like RC-5, SIRC, are used to communicate with infrared.

Free space optical communication using infrared lasers can be a relatively inexpensive way to install a communications link in an urban area operating at up to 4 gigabit/s, compared to the cost of burying fiber optic cable, except for the radiation damage. "Since the eye cannot detect IR, blinking or closing the eyes to help prevent or reduce damage may not happen."

Infrared lasers are used to provide the light for optical fiber communications systems. Infrared light with a wavelength around 1,330 nm (least dispersion) or 1,550 nm (best transmission) are the best choices for standard silica fibers.

IR data transmission of encoded audio versions of printed signs is being researched as an aid for visually impaired people through the RIAS (Remote Infrared Audible Signage) project. Transmitting IR data from one device to another is sometimes referred to as beaming.

Spectroscopy
Infrared vibrational spectroscopy (see also near-infrared spectroscopy) is a technique that can be used to identify molecules by analysis of their constituent bonds. Each chemical bond in a molecule vibrates at a frequency characteristic of that bond. A group of atoms in a molecule (e.g., CH2) may have multiple modes of oscillation caused by the stretching and bending motions of the group as a whole. If an oscillation leads to a change in dipole in the molecule then it will absorb a photon that has the same frequency. The vibrational frequencies of most molecules correspond to the frequencies of infrared light. Typically, the technique is used to study organic compounds using light radiation from the mid-infrared, 4,000–400 cm−1. A spectrum of all the frequencies of absorption in a sample is recorded. This can be used to gain information about the sample composition in terms of chemical groups present and also its purity (for example, a wet sample will show a broad O-H absorption around 3200 cm−1). The unit for expressing radiation in this application, cm−1, is the spectroscopic wavenumber. It is the frequency divided by the speed of light in vacuum.

Thin film metrology
In the semiconductor industry, infrared light can be used to characterize materials such as thin films and periodic trench structures. By measuring the reflectance of light from the surface of a semiconductor wafer, the index of refraction (n) and the extinction Coefficient (k) can be determined via the Forouhi–Bloomer dispersion equations. The reflectance from the infrared light can also be used to determine the critical dimension, depth, and sidewall angle of high aspect ratio trench structures.

Meteorology
Weather satellites equipped with scanning radiometers produce thermal or infrared images, which can then enable a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features. The scanning is typically in the range 10.3–12.5 μm (IR4 and IR5 channels).

Clouds with high and cold tops, such as cyclones or cumulonimbus clouds, are often displayed as red or black, lower warmer clouds such as stratus or stratocumulus are displayed as blue or grey, with intermediate clouds shaded accordingly. Hot land surfaces are shown as dark-grey or black. One disadvantage of infrared imagery is that low cloud such as stratus or fog can have a temperature similar to the surrounding land or sea surface and does not show up. However, using the difference in brightness of the IR4 channel (10.3–11.5 μm) and the near-infrared channel (1.58–1.64 μm), low cloud can be distinguished, producing a fog satellite picture. The main advantage of infrared is that images can be produced at night, allowing a continuous sequence of weather to be studied.

These infrared pictures can depict ocean eddies or vortices and map currents such as the Gulf Stream, which are valuable to the shipping industry. Fishermen and farmers are interested in knowing land and water temperatures to protect their crops against frost or increase their catch from the sea. Even El Niño phenomena can be spotted. Using color-digitized techniques, the gray-shaded thermal images can be converted to color for easier identification of desired information.

The main water vapour channel at 6.40 to 7.08 μm can be imaged by some weather satellites and shows the amount of moisture in the atmosphere.

Climatology
In the field of climatology, atmospheric infrared radiation is monitored to detect trends in the energy exchange between the Earth and the atmosphere. These trends provide information on long-term changes in Earth's climate. It is one of the primary parameters studied in research into global warming, together with solar radiation.

A pyrgeometer is utilized in this field of research to perform continuous outdoor measurements. This is a broadband infrared radiometer with sensitivity for infrared radiation between approximately 4.5 μm and 50 μm.

Astronomy
Astronomers observe objects in the infrared portion of the electromagnetic spectrum using optical components, including mirrors, lenses and solid state digital detectors. For this reason it is classified as part of optical astronomy. To form an image, the components of an infrared telescope need to be carefully shielded from heat sources, and the detectors are chilled using liquid helium.

The sensitivity of Earth-based infrared telescopes is significantly limited by water vapor in the atmosphere, which absorbs a portion of the infrared radiation arriving from space outside of selected atmospheric windows. This limitation can be partially alleviated by placing the telescope observatory at a high altitude, or by carrying the telescope aloft with a balloon or an aircraft. Space telescopes do not suffer from this handicap, and so outer space is considered the ideal location for infrared astronomy.

The infrared portion of the spectrum has several useful benefits for astronomers. Cold, dark molecular clouds of gas and dust in our galaxy will glow with radiated heat as they are irradiated by imbedded stars. Infrared can also be used to detect protostars before they begin to emit visible light. Stars emit a smaller portion of their energy in the infrared spectrum, so nearby cool objects such as planets can be more readily detected. (In the visible light spectrum, the glare from the star will drown out the reflected light from a planet.)

Infrared light is also useful for observing the cores of active galaxies, which are often cloaked in gas and dust. Distant galaxies with a high redshift will have the peak portion of their spectrum shifted toward longer wavelengths, so they are more readily observed in the infrared.

Cleaning
Infrared cleaning is a technique used by some motion picture film scanners, film scanners and flatbed scanners to reduce or remove the effect of dust and scratches upon the finished scan. It works by collecting an additional infrared channel from the scan at the same position and resolution as the three visible color channels (red, green, and blue). The infrared channel, in combination with the other channels, is used to detect the location of scratches and dust. Once located, those defects can be corrected by scaling or replaced by inpainting.

Art conservation and analysis
Infrared reflectography can be applied to paintings to reveal underlying layers in a non-destructive manner, in particular the artist's underdrawing or outline drawn as a guide. Art conservators use the technique to examine how the visible layers of paint differ from the underdrawing or layers in between (such alterations are called pentimenti when made by the original artist). This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti, the more likely a painting is to be the prime version. It also gives useful insights into working practices. Reflectography often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting.

Recent progress in the design of infrared-sensitive cameras makes it possible to discover and depict not only underpaintings and pentimenti, but entire paintings that were later overpainted by the artist. Notable examples are Picasso's Woman Ironing and Blue Room, where in both cases a portrait of a man has been made visible under the painting as it is known today.

Similar uses of infrared are made by conservators and scientists on various types of objects, especially very old written documents such as the Dead Sea Scrolls, the Roman works in the Villa of the Papyri, and the Silk Road texts found in the Dunhuang Caves. Carbon black used in ink can show up extremely well.

Biological systems

The pit viper has a pair of infrared sensory pits on its head. There is uncertainty regarding the exact thermal sensitivity of this biological infrared detection system.

Other organisms that have thermoreceptive organs are pythons (family Pythonidae), some boas (family Boidae), the Common Vampire Bat (Desmodus rotundus), a variety of jewel beetles (Melanophila acuminata), darkly pigmented butterflies (Pachliopta aristolochiae and Troides rhadamantus plateni), and possibly blood-sucking bugs (Triatoma infestans). By detecting the heat that their prey emits, crotaline and boid snakes identify and capture their prey using their IR-sensitive pit organs. Comparably, IR-sensitive pits on the Common Vampire Bat (Desmodus rotundus) aid in the identification of blood-rich regions on its warm-blooded victim. The jewel beetle, Melanophila acuminata, locates forest fires via infrared pit organs, where on recently burnt trees, they deposit their eggs. Thermoreceptors on the wings and antennae of butterflies with dark pigmentation, such Pachliopta aristolochiae and Troides rhadamantus plateni, shield them from heat damage as they sunbathe in the sun. Additionally, it's hypothesised that thermoreceptors let bloodsucking bugs (Triatoma infestans) locate their warm-blooded victims by sensing their body heat.

Some fungi like Venturia inaequalis require near-infrared light for ejection.

Although near-infrared vision (780–1,000 nm) has long been deemed impossible due to noise in visual pigments, sensation of near-infrared light was reported in the common carp and in three cichlid species. Fish use NIR to capture prey and for phototactic swimming orientation. NIR sensation in fish may be relevant under poor lighting conditions during twilight and in turbid surface waters.

Photobiomodulation
Near-infrared light, or photobiomodulation, is used for treatment of chemotherapy-induced oral ulceration as well as wound healing. There is some work relating to anti-herpes virus treatment. Research projects include work on central nervous system healing effects via cytochrome c oxidase upregulation and other possible mechanisms.

Health hazards
Strong infrared radiation in certain industry high-heat settings may be hazardous to the eyes, resulting in damage or blindness to the user. Since the radiation is invisible, special IR-proof goggles must be worn in such places.

Scientific history
The discovery of infrared radiation is ascribed to William Herschel, the astronomer, in the early 19th century. Herschel published his results in 1800 before the Royal Society of London. Herschel used a prism to refract light from the sun and detected the infrared, beyond the red part of the spectrum, through an increase in the temperature recorded on a thermometer. He was surprised at the result and called them "Calorific Rays". The term "infrared" did not appear until late 19th century. An earlier experiment in 1790 by Marc-Auguste Pictet demonstrated the reflection and focusing of radiant heat via mirrors in the absence of visible light.

Other important dates include:
 * 1830: Leopoldo Nobili made the first thermopile IR detector.
 * 1840: John Herschel produces the first thermal image, called a thermogram.
 * 1860: Gustav Kirchhoff formulated the blackbody theorem $$E = J(T, n)$$. See:
 * English translation:
 * 1873: Willoughby Smith discovered the photoconductivity of selenium.
 * 1878: Samuel Pierpont Langley invents the first bolometer, a device which is able to measure small temperature fluctuations, and thus the power of far infrared sources.
 * 1879: Stefan–Boltzmann law formulated empirically that the power radiated by a blackbody is proportional to T4.
 * 1880s and 1890s: Lord Rayleigh and Wilhelm Wien solved part of the blackbody equation, but both solutions diverged in parts of the electromagnetic spectrum. This problem was called the "ultraviolet catastrophe and infrared catastrophe".
 * 1892: Willem Henri Julius published infrared spectra of 20 organic compounds measured with a bolometer in units of angular displacement.
 * 1901: Max Planck published the blackbody equation and theorem. He solved the problem by quantizing the allowable energy transitions.
 * 1905: Albert Einstein developed the theory of the photoelectric effect.
 * 1905–1908: William Coblentz published infrared spectra in units of wavelength (micrometers) for several chemical compounds in Investigations of Infra-Red Spectra.
 * 1917: Theodore Case developed the thallous sulfide detector, which helped produce the first infrared search and track device able to detect aircraft at a range of one mile (1.6 km).
 * 1935: Lead salts – early missile guidance in World War II.
 * 1938: Yeou Ta predicted that the pyroelectric effect could be used to detect infrared radiation.
 * 1945: The Zielgerät 1229 "Vampir" infrared weapon system was introduced as the first portable infrared device for military applications.
 * 1952: Heinrich Welker grew synthetic InSb crystals.
 * 1950s and 1960s: Nomenclature and radiometric units defined by Fred Nicodemenus, G. J. Zissis and R. Clark; Robert Clark Jones defined D*.
 * 1958: W. D. Lawson (Royal Radar Establishment in Malvern) discovered IR detection properties of Mercury cadmium telluride (HgCdTe).
 * 1958: Falcon and Sidewinder missiles were developed using infrared technology.
 * 1960s: Paul Kruse and his colleagues at Honeywell Research Center demonstrate the use of HgCdTe as an effective compound for infrared detection.
 * 1962: J. Cooper demonstrated pyroelectric detection.
 * 1964: W. G. Evans discovered infrared thermoreceptors in a pyrophile beetle.
 * 1965: First IR handbook; first commercial imagers (Barnes, Agema (now part of FLIR Systems Inc.)); Richard Hudson's landmark text; F4 TRAM FLIR by Hughes; phenomenology pioneered by Fred Simmons and A. T. Stair; U.S. Army's night vision lab formed (now Night Vision and Electronic Sensors Directorate (NVESD)), and Rachets develops detection, recognition and identification modeling there.
 * 1970: Willard Boyle and George E. Smith proposed CCD at Bell Labs for picture phone.
 * 1973: Common module program started by NVESD.
 * 1978: Infrared imaging astronomy came of age, observatories planned, IRTF on Mauna Kea opened; 32 × 32 and 64 × 64 arrays produced using InSb, HgCdTe and other materials.
 * 2013: On 14 February, researchers developed a neural implant that gives rats the ability to sense infrared light, which for the first time provides living creatures with new abilities, instead of simply replacing or augmenting existing abilities.
 * 1978: Infrared imaging astronomy came of age, observatories planned, IRTF on Mauna Kea opened; 32 × 32 and 64 × 64 arrays produced using InSb, HgCdTe and other materials.
 * 2013: On 14 February, researchers developed a neural implant that gives rats the ability to sense infrared light, which for the first time provides living creatures with new abilities, instead of simply replacing or augmenting existing abilities.

title: Infrared


text:
Icosidodecahedron

In geometry, an icosidodecahedron or pentagonal gyrobirotunda is a polyhedron with twenty (icosi) triangular faces and twelve (dodeca) pentagonal faces. An icosidodecahedron has 30 identical vertices, with two triangles and two pentagons meeting at each, and 60 identical edges, each separating a triangle from a pentagon. As such, it is one of the Archimedean solids and more particularly, a quasiregular polyhedron.

Construction
One way to construct the icosidodecahedron is to start with two pentagonal rotunda by attaching them to their bases. These rotundas cover their decagonal base so that the resulting polyhedron has 32 faces, 30 vertices, and 60 edges. This construction is similar to one of the Johnson solids, the pentagonal orthobirotunda. The difference is that the icosidodecahedron is constructed by twisting its rotundas by 36°, a process known as gyration, resulting in the pentagonal face connecting to the triangular one. The icosidodecahedron has an alternative name, pentagonal gyrobirotunda.

Convenient Cartesian coordinates for the vertices of an icosidodecahedron with unit edges are given by the even permutations of: $$ (0, 0, \pm \varphi), \qquad \left(\pm \frac{1}{2}, \pm \frac{\varphi}{2}, \pm \frac{\varphi^2}{2} \right), $$ where $$ \varphi $$ denotes the golden ratio.

Properties
The surface area of an icosidodecahedron $$ A $$ can be determined by calculating the area of all pentagonal faces. The volume of an icosidodecahedron $$ V $$ can be determined by slicing it off into two pentagonal rotunda, after which summing up their volumes. Therefore, its surface area and volume can be formulated as: $$\begin{align} A &= \left(5\sqrt{3}+3\sqrt{25+10\sqrt{5}}\right) a^2 &\approx 29.306a^2 \\ V &= \frac{45+17\sqrt{5}}{6}a^3 &\approx 13.836a^3. \end{align}$$

The dihedral angle of an icosidodecahedron between pentagon-to-triangle is $$ \arccos \left(-\sqrt{\frac{5 + 2\sqrt{5}}{15}} \right) \approx 142.62^\circ, $$ determined by calculating the angle of a pentagonal rotunda.

An icosidodecahedron has icosahedral symmetry, and its first stellation is the compound of a dodecahedron and its dual icosahedron, with the vertices of the icosidodecahedron located at the midpoints of the edges of either.

The icosidodecahedron is an Archimedean solid, meaning it is a highly symmetric and semi-regular polyhedron, and two or more different regular polygonal faces meet in a vertex. The polygonal faces that meet for every vertex are two equilateral triangles and two regular pentagons, and the vertex figure of an icosidodecahedron is $$ (3 \cdot 5)^2 = 3^2 \cdot 5^2 $$. Its dual polyhedron is rhombic triacontahedron, a Catalan solid.

The icosidodecahedron has 6 central decagons. Projected into a sphere, they define 6 great circles. used these 6 great circles, along with 15 and 10 others in two other polyhedra to define his 31 great circles of the spherical icosahedron.

The long radius (center to vertex) of the icosidodecahedron is in the golden ratio to its edge length; thus its radius is $$ \varphi $$ if its edge length is 1, and its edge length is $$ 1/\varphi $$ if its radius is 1. Only a few uniform polytopes have this property, including the four-dimensional 600-cell, the three-dimensional icosidodecahedron, and the two-dimensional decagon. (The icosidodecahedron is the equatorial cross-section of the 600-cell, and the decagon is the equatorial cross-section of the icosidodecahedron.) These radially golden polytopes can be constructed, with their radii, from golden triangles which meet at the center, each contributing two radii and an edge.

Related polytopes
The icosidodecahedron is a rectified dodecahedron and also a rectified icosahedron, existing as the full-edge truncation between these regular solids.

The icosidodecahedron contains 12 pentagons of the dodecahedron and 20 triangles of the icosahedron:

The icosidodecahedron exists in a sequence of symmetries of quasiregular polyhedra and tilings with vertex configurations (3.n)2, progressing from tilings of the sphere to the Euclidean plane and into the hyperbolic plane. With orbifold notation symmetry of *n32 all of these tilings are wythoff construction within a fundamental domain of symmetry, with generator points at the right angle corner of the domain.

Related polyhedra
The truncated cube can be turned into an icosidodecahedron by dividing the octagons into two pentagons and two triangles. It has pyritohedral symmetry.

Eight uniform star polyhedra share the same vertex arrangement. Of these, two also share the same edge arrangement: the small icosihemidodecahedron (having the triangular faces in common), and the small dodecahemidodecahedron (having the pentagonal faces in common). The vertex arrangement is also shared with the compounds of five octahedra and of five tetrahemihexahedra.

Related polychora
In four-dimensional geometry, the icosidodecahedron appears in the regular 600-cell as the equatorial slice that belongs to the vertex-first passage of the 600-cell through 3D space. In other words: the 30 vertices of the 600-cell which lie at arc distances of 90 degrees on its circumscribed hypersphere from a pair of opposite vertices, are the vertices of an icosidodecahedron. The wireframe figure of the 600-cell consists of 72 flat regular decagons. Six of these are the equatorial decagons to a pair of opposite vertices, and these six form the wireframe figure of an icosidodecahedron.

If a 600-cell is stereographically projected to 3-space about any vertex and all points are normalised, the geodesics upon which edges fall comprise the icosidodecahedron's barycentric subdivision.

Graph

The skeleton of an icosidodecahedron can be represented as the graph with 30 vertices and 60 edges, one of the Archimedean graphs. It is quartic, meaning that each of its vertex is connected by four other vertices.

Appearance
The icosidodecahedron may appears in structural, as in the geodesic dome of the Hoberman sphere.

Icosidodecahedra can be found in all eukaryotic cells, including human cells, as Sec13/31 COPII coat-protein formations.

The icosidodecahedron may also found in popular culture. In Star Trek universe, the Vulcan game of logic Kal-Toh has the goal of creating a shape with two nested holographic icosidodecahedra joined at the midpoints of their segments.

title: Icosidodecahedron