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Reflection dependence from wavelenght

  1. May 18, 2016 #1
    1. The problem statement, all variables and given/known data
    Hi guys, I have this exercise and I m confused.
    Incident (white light) light ray is perpendicular to glass surface , glass plate is 0,4microm thick. Which wavelengths in reflected ray becomes more intense?

    2. Relevant equations

    3. The attempt at a solution
    So i know that light is refracted on the surface of 2 different mediums, different wavelengths are refracted in different angles.
    But i do not know nothing about wavelength and/or intensity dependence from reflection. And its seems weird that intensity of some wavelengths increases after reflection.

    Could someone,please, help?
    Maybe some tips about which physical phenomenon I should study?
  2. jcsd
  3. May 18, 2016 #2


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    Homework Helper

    Think of interference. For which wavelength is constructive interference in the reflected light?
  4. May 18, 2016 #3
    Thank you for your reply
    Ok, I think I go it.
    First I calculate the angle of light ray inside the glass from Snell's law.
    Second I use Thin films equation for constructive interference and calculate the wavelengths by altering m in the formula.
  5. May 18, 2016 #4


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    Homework Helper

    No need to calculate the angle, as the incidence is perpendicular, that is, the angle of incidence is 0 degree. The refracted ray does not change direction.
    The second plan is correct, find the condition for constructive interference for reflected light and select the wavelength by altering m.
  6. May 18, 2016 #5
    OK, thank you again for help!
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