Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Looking through glass

  1. Jan 31, 2006 #1
    If light reflects from all surfaces, why is the view through a glass window not noticeably dimmer than the view with the window open?

    Can someone give me som hint? I know glass has a refractive index of 1.5...
     
  2. jcsd
  3. Jan 31, 2006 #2

    Mk

    User Avatar

    The glass does not absorb very much light, and does not reflect very much light.

    A strawberry absorbs wavelength's other than red. That is why it looks red to you.

    A black object absorbs most of the light that comes at it, so it looks black.
     
  4. Feb 1, 2006 #3

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Ordinary glass DOES absorbs light, espeically in the UV range. We pay a lot of money to get quartz and fused silica to let UV light passes through. There's no material that I know off that lets light of all frequency to pass through.

    Zz.
     
  5. Feb 1, 2006 #4
    this is fresnel relaction, as you can see the percent of reflection is very small.

    [tex]R=(\frac{n_1-n_0}{n_1+n_0})^2[/tex]

    but this is just the classical vies of things, (its pretty accurate, but feyman got it better)
     
    Last edited: Feb 1, 2006
  6. Feb 1, 2006 #5
    It IS dimmer, just not necessarily "noticable" through "human" eyes. I know of no glass(or any substance for that matter) that transmits light with no loss.
     
  7. Feb 1, 2006 #6

    Claude Bile

    User Avatar
    Science Advisor

    Our eyes are logarithmic detectors - that is, they are capable of measuring light intensities over many orders of magnitude. As such, a 4% change in intensity (typical for air-glass reflection) is not readily apparent to the naked eye, as it would be for a linear detector such as a photodiode.

    Claude.
     
  8. Feb 1, 2006 #7
    I guess that's why I can't get a tan through the window...:tongue2:
     
  9. Feb 2, 2006 #8
    Why would we want glass to transmit UV?
    Don't we want to protect ourselves from UV radiation? (it may cause sunburn! :redface:)
     
  10. Feb 2, 2006 #9

    Mk

    User Avatar

  11. Feb 2, 2006 #10

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I have a laser that is in the UV range. But my experiment is done in ultra-high vacuum. I'll give you ONE guess on why I would need a fused silica window somewhere on my vacuum chamber.

    Zz.
     
  12. Feb 2, 2006 #11

    DaveC426913

    User Avatar
    Gold Member

    The Newtonian telescope is based on the fact that glass does absorb light.

    A Newtonian is different from other types of telescopes in that it uses mirrors rather than lenses. Every lens the light passes through costs you a fraction of precious, precious brightness, which is what astronomy is all about.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Looking through glass
  1. See-through glass (Replies: 11)

  2. Light through glass ? (Replies: 2)

Loading...