1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why does an object appear darker when wet?.

  1. Jan 13, 2012 #1
    My Question is just that of the title of the thread;namely, why does something get darker when wet? Does it have to do with the refractive index of water? Or is it something else altogether? Thanks for you help!
     
  2. jcsd
  3. Jan 13, 2012 #2
    The rough dry surface (say a road) scatters light all over because of the roughness. When it's wet the water is a much smoother surface and only reflects light in a much more straight way like a mirror. Your headlights won't scatter back toward you as easily. Same with a peice of rubber or wood.
     
  4. Jan 13, 2012 #3

    DaveC426913

    User Avatar
    Gold Member

    That was the answer I started to give (surface roughness). But I checked by Googling. Overwhelmingly, it seems that may not be the answer at all. It seems to be much more about water resulting in a higher amount of refraction rather than reflection.
     
  5. Jan 13, 2012 #4
    Theres some truth to it; water can act a little like an antireflective coating but this is not the main effect. To see this, wet a polished surface like a tumbled stone. It won't get darker. Marble countertop if you have it in the kitchen and it's polished is easy to try.
     
  6. Jan 13, 2012 #5

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

  7. Dec 10, 2013 #6
    Absorption Frequencies!

    I think there is an other reason for this phenomenon. When an object seems blue, it means that the frequencies of oscilations between molecules of that object are different from blue spectrum of light frequency and all other colors absorb except blue. If an object become wet, the forces between water molecules and that object, make new forces and these new forces make new frequencies. So there is more frequencies to absorb by that object and that object will appear darker.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook