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Thread: Visible light spectrum

  1. #1 Visible light spectrum 
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    I have a book at home written by McMurry Fay and it says the visible light spectrum is 380 nm - 780 nm, the book we have at school says 400 nm - 700 nm. Which is right?


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  3. #2 Re: Visible light spectrum 
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    Quote Originally Posted by DragonX556
    I have a book at home written by McMurry Fay and it says the visible light spectrum is 380 nm - 780 nm, the book we have at school says 400 nm - 700 nm. Which is right?
    I believe it's 380nm-780nm. (Wikipedia)


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    The range for human eyes is just under 1 octave, I suggest the wider figures you have there are across all creatures the narrower 400-700 is the human range.

    I think you might have read "Visible light is etc" in one and "Human response etc.." in the other.
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    Usually you can trust figures that bother to be more accurate over figures that are just rounded (like the school textbooks). So I'm going with 380-780.
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  6. #5  
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    Here's what Wikipedia says: "There are no exact bounds to the visible spectrum; a typical human eye will respond to wavelengths in air from 400 to 700 nm, although some people may be able to perceive wavelengths from 380 to 780 nm."
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    By the way, "visible light" is a pleonasm (like "large giant" or "hot fire"). All light is visible, and all visible radiation is light, because that's the definition of "light". That's also why there is no such thing as "infrared light" or "UV light" (it's UV radiation) although these terms have become annoyingly common in colloquial language. Hey, I just like to throw in my mildly irrelevant comments. :-D
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    Quote Originally Posted by The P-manator
    Usually you can trust figures that bother to be more accurate over figures that are just rounded (like the school textbooks). So I'm going with 380-780.
    yeah, that's a really good point. All through Chem in school i thought the electronegativity of oxygen was 3.5, and that of Fluorine 4.0, and then elsewhere, more recently, i've seen 3.44 and 3.98, respectively. And i've seen the bond angle of water molecules between 105<sup>o</sup> and 104.45<sup>o</sup>
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    Quote Originally Posted by Harold14370
    Here's what Wikipedia says: "There are no exact bounds to the visible spectrum; a typical human eye will respond to wavelengths in air from 400 to 700 nm, although some people may be able to perceive wavelengths from 380 to 780 nm."
    I believe that to be true because I can very slightly see infra-red.
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    Quote Originally Posted by leohopkins
    I believe that to be true because I can very slightly see infra-red.
    Really! That's cool. 8)
    Oh, wait a moment.
    No it isn't. It's hot.
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  11. #10 Re: Visible light spectrum 
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    Quote Originally Posted by DragonX556
    I have a book at home written by McMurry Fay and it says the visible light spectrum is 380 nm - 780 nm, the book we have at school says 400 nm - 700 nm. Which is right?
    If you look at this image, you can establish yourself which wavelengths your own eyes can see:
    http://en.wikipedia.org/wiki/Image:S...41pxWithnm.png
    About wavelengths much shorter than 400, it's not possible to say, because the image doesn't allow it. About those greater than 700, I can perceive quite well up to ~ 740 nm.
    And you?
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    I think I can see around 740nm also although it is hard to tell whether or not you are imagining it!
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  13. #12  
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    If you look at this image, you can establish yourself which wavelengths your own eyes can see:
    http://en.wikipedia.org/wiki/Image:S...41pxWithnm.png
    About wavelengths much shorter than 400, it's not possible to say, because the image doesn't allow it. About those greater than 700, I can perceive quite well up to ~ 740 nm.
    And you?
    Wow, I can see beyond 800 nm, does that mean I am a freak? I also noticed that my eyes work much better, when I adjust the brightness and contrast on my monitor.

    Do you really think this picture shows a spectrum of varying wave-length at uniform intensity? Ouch... yes... I touched the dark-red part... it does feel pretty hot. lol
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  14. #13  
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    Quote Originally Posted by M
    By the way, "visible light" is a pleonasm (like "large giant" or "hot fire"). All light is visible, and all visible radiation is light, because that's the definition of "light". That's also why there is no such thing as "infrared light" or "UV light" (it's UV radiation) although these terms have become annoyingly common in colloquial language. Hey, I just like to throw in my mildly irrelevant comments. :-D
    That all depends on your definition of light. In a more technical sense light is referred to as electromagnetic radiation of any wavelength.
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  15. #14  
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    Quote Originally Posted by M
    Wow, I can see beyond 800 nm, does that mean I am a freak?
    Probably!
    I also noticed that my eyes work much better, when I adjust the brightness and contrast on my monitor.
    I have a CRT "LG Flatron 795FT Plus" Monitor; which is yours?
    Do you really think this picture shows a spectrum of varying wave-length at uniform intensity?
    Certainly not. But it's the best I've found. This doesn't imply it's extremely good, of course. Furthermore, it obviously depends on your monitor characteristics (one of which you have already discovered!)
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