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Angular spread of light rays passing through a prism

  1. Apr 18, 2017 #1
    1. The problem statement, all variables and given/known data
    The problem asks:
    The index of refraction for violet light in silica flint glass is 1.66, and the index of refraction for red light is 1.62. What is the angular spread of visible light passing through a prism of apex angle 60 degrees if the angle of incidence is 50.03 degrees?


    2. Relevant equations
    n1=1.62
    n2=1.66
    n =1
    theta1=50.03
    Angular spread= arcsin[n*sin(theta1)/n1] - arcsin[n*sin(theta1)/n2]


    3. The attempt at a solution
    I plugged in my numbers into the equation above and got:

    Angular spread= arcsin[1*sin(50.03)/1.62] - arcsin[1*sin(50.03)/1.66]

    and got: 0.7388

    but that was wrong...so where did I go wrong?
     
  2. jcsd
  3. Apr 18, 2017 #2

    BvU

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    0.7388 radians seems a bit much... Maybe you mean degrees :smile: ? Is that for the entrance into the glass only ?
     
  4. Apr 18, 2017 #3
    yeah sorry, i meant degrees :P the question wants the answers in degrees too
    is the 60 degree number important? if so where do i use it?
     
  5. Apr 18, 2017 #4

    BvU

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    You might use it on the other side of the prism to calculate the angle of incidence there...

    Thing to do: make a drawing indicating the various angles...
     
  6. Apr 18, 2017 #5
    Could you show me what you mean by that?
     
  7. Apr 19, 2017 #6

    Ibix

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    @Quenton Robertson - this is, I think, the key point.
     
  8. Apr 19, 2017 #7

    BvU

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    Maybe QR missed my second line in #4 (I first posted a one-liner :smile:)
     
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