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How far does red light travel.

  1. Apr 5, 2009 #1
    Hey, I have heard that red light travels shorter than regular light. I am thinking of flashlights, where I learned that people in the army uses red light to make them less visible. Is this true?
     
  2. jcsd
  3. Apr 5, 2009 #2

    clem

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    It is not true. The army uses infrared light for "night vision" because the light can't be seen by the enemy. The soldiers need special equipment that makes the infrared visible to them. The distance the light travels has nothing to do with it.
     
  4. Apr 5, 2009 #3
    Thanks.
     
  5. Apr 5, 2009 #4
    Why does the sun look reddish at sunrise and sunset?
     
  6. Apr 5, 2009 #5
    Because the sun is being turned off/on at those times, since it doesn't shine during the night. Like, duh.
     
  7. Apr 5, 2009 #6

    clem

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    The atmosphere scatters blue light more than red light. At sunrise and sunset, you see the light coming toward you with much of its blue component scattered away.
    The blue sky you when you don't look directly at the sun (which would blind you) is the scattered blue light.
     
  8. Apr 5, 2009 #7
    I don't know if this helps, but red light illuminated within, say, an aircraft cockpit, allows visual response to controls and paperwork without over-stimulation to the eyes.
     
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