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  1. keannu's Avatar
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    #1

    ultraviolet vs infrared

    I think "ultra" in "ultraviolet" means "exceeding or beyond or outside of " something(violet color), so does "infra" in "infrared" mean the same thing? Do they use "infra" as "exceeding" a lot?

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    #2

    Re: ultraviolet vs infrared

    I have heard "ultra" used in other contexts to mean "exceeding or beyond or outside of".

    I have never heard "infra" used to mean "exceeding or beyond or outside of".

  2. MikeNewYork's Avatar
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    #3

    Re: ultraviolet vs infrared

    Quote Originally Posted by keannu View Post
    I think "ultra" in "ultraviolet" means "exceeding or beyond or outside of " something(violet color), so does "infra" in "infrared" mean the same thing? Do they use "infra" as "exceeding" a lot?
    Infra has a meaning different from ultra.

    These words refer to wavelengths of light outside the visible spectrum. Ultraviolet is beyond violet on the light scale. "Infra" means below or under, so infrared is under red on the other end of the visible spectrum.

    The visible light spectrum (colors) are usually described as red - orange - yellow - green - blue - indigo - violet (mnemonic = ROY G BIV). Ultraviolet would be at the right end of that chart and infrared would be at the left.

  3. keannu's Avatar
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    #4

    Re: ultraviolet vs infrared

    I think "ultraviolet" as "exceeding" and "infrared" as "under" are not compatible sets in the light spectrum concept. The sets should be either horizontally "exceeding" or vertically "over+under". Maybe "ultra" means vertical "over".
    And I have found another definition of "infra" as exceeding in a Korean-English dictionary(infra- : ??? ????, but not in an English-English one.

  4. probus's Avatar
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    #5
    The Latin root words ultra and infra mean above and below respectively. Ultraviolet and infrared are scientific terms for electromagnetic radiation just beyond the range of frequencies that human eyes can see. Ultraviolet rays are those whose frequencies are slightly above that of violet light, while infrared rays have frequencies a little below that of red light. Think back to your school days: the colours of the visible spectrum are red, orange, yellow, green, blue and violet, in order of increasing frequency.

    In electromagnetic radiation, frequency and wavelength are inversely proportional. Therefore waves can be specifically described by wavelength just as well as by frequency. Often wavelength is easier to measure, so people tend to use wavelength in describing radiation. But they still use the terms ultraviolet and infrared as I said above, thus inverting the natural meanings of ultra and infra.

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