The answer should be ?

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1 Answer
Jun 2, 2018

#sin(90^circ-p)/sin(90^circ -q)= cos p/cos q#

Explanation:

The angles of incidence and refraction that appear in Snell's law are measured from the normal. It is easy to see that they are #90^circ-p# and #90^\circ -q# , respectively.

So, the refractive index of the glass block is

#sin(90^circ-p)/sin(90^circ -q)#