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Light travels in water and not through opaque objects?

  1. Jul 30, 2015 #1
    I want to know, why does light travel through water, glass etc and does not travel through opaque objects like wall, floor etc?
  2. jcsd
  3. Jul 30, 2015 #2
    Opaque materials are absorbing the incoming photons, (and in doing so the material becomes slightly warmer).
    Transparent materials allow some photons to pass through without being absorbed, but no material is perfectly transparent, if it is made thick enough an appreciable amount of photons still are absorbed.
  4. Jul 30, 2015 #3
    Why does glass doesn't absorb photons whereas opaque materials do?
  5. Jul 30, 2015 #4
    While glass has transparency for visible light, it is opaque for UV light.
    The reason why glass and some other materials permit some photons to pass through is because due the atomic composition of the material, the incoming photon has less liklyhood of being energetic enough to kick an electron into a higher energy state, (ie it is less likely to be absorbed).
  6. Jul 30, 2015 #5


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    have a look at this video ....
  7. Jul 30, 2015 #6


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    The explanation is a bit too simple in the clip. He is talking in terms of discrete Energy Levels when they don't actually exist in condensed matter. There are Energy Bands in solids and not states. It would have been better to have said that, in a transparent substance, the next highest band is too high in energy for the electron to become excited into it.
    Discrete energy states only occur in isolated atoms (in low pressure gases, aamof)
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