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Why the sky is blue and not violet

  1. Sep 3, 2015 #1
    Though the intensity of violet light is more than that of blue we see the sky blue.Why this happens?Does it happen only for that our eyes are more sensible towards blue light than violet light or due to absorption of violet light by Ozone layer? And why different light waves having different intensity produce different sensation in our eyes?
  2. jcsd
  3. Sep 3, 2015 #2


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    This question has been asked many times on PF. Please see the links that appear below under "Similar discussions." For instance, you could check out Why the sky is blue and not violet, which has exactly the same title as your thread.
  4. Sep 3, 2015 #3


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    Our colour vision relies precisely on this. We have three sets of receptors that have varying sensitivities over the range of visible radiation and our brain takes in the combination of outputs from the three sensors and 'categorises' them into colours (Search Tristimulus Colour Vision theory"). The sensitivity of the sensors to wavelengths corresponding to Violet is very low (it's right on the 'skirts' of sensitivity). Also, the spectrum of Sunlight is relatively low in Violet content so we just don't care too much about Violet (in a manner of speaking) and doesn't discriminate too much. If you change the amount of the 'violet wavelengths' in the light entering the eye, it will make very little difference to the perceived colour; the colour that the brain assigns to what is seen.
    OTOH, there are other wavelengths to which the eye/brain are much more discriminating about.
    There is an analogous thing in our perception of musical pitch. We have very poor discrimination of musical notes at the extremens of our audible frequency range, compared with our discrimination in the mid range. (You can replace the very highest and lowest audible frequencies with hisses and thumps without spoiling the listening experience too much.
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