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Homework Help: Optics- Total internal reflection

  1. Jan 17, 2010 #1
    A small source of light at the bottom face of a rectangular glass slab 2.25 cm thick is viewed from above. Rays of light totally internally reflected at the top of the surface outline a circle of 7.6cm in diameter in the bottom surface. Determine the refraction index of the glass.

    This is what I interpreted:

    I can find out the angle of incidence and reflection (theta 1), but then I am stuck. please help.
  2. jcsd
  3. Jan 18, 2010 #2


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    My understanding is that the light source is at the bottom. Light is emitted, strikes the top surface where it is reflected at some angle, and returns to the bottom surface. The light source and 7.6 cm circle are both at the bottom surface.

    The words "viewed from above" seem misleading and irrelevant.
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