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[Refraction] Light and prisms

  1. Nov 26, 2011 #1
    1. The problem statement, all variables and given/known data

    A beam of light falls perpendicularly on the surface of a triangular prism.
    Draw the beams path through the prism. Show any necessary calculations.
    n = 1.5

    2. Relevant equations

    n1sin(a) = n2sin(b)

    maybe, not sure tbh.

    3. The attempt at a solution

    This is what I did to find the angles:

    1.5 = sin 90°/sin(b)

    1.5 sin(b) = sin 90°

    sin (b) = sin 90° /1.5

    sin (b) = sin-1 0.66

    b = 41.8°

    I have no idea whether I'm right or not, I asked my teacher how to do it but she did it in a hurry so I didnt understand what she was talking about.
  2. jcsd
  3. Nov 26, 2011 #2


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    Homework Helper

    When the light falls perpendicular to the surface of an equilateral prism, it goes undeviating through the surface.The angle of incident on the other face is equal to the angle of prism.
  4. Nov 27, 2011 #3


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    The angle of incidence and the angle of refraction both are measured with respect to the normal of the interface. If the ray falls perpendicularly to the surface, the angle of incidence is zero. According to Snell's law (your first equation) the angle of refraction is the same zero. The direction of the ray stays unchanged when it enters the prism. Find the angle it strikes the other side of the prism.

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