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Question:

In an experiment for determination of refractive index of glass of a prism, it was found that a ray incident at angle 35° suffers a deviation of 40° and that it emerges at angle 79°. In that case, which of the following is closest to the maximum possible value of the refractive index?

1.7

1.6

1.8

1.5

Solution:

δ = 40°, i = 35°, e = 79°
Since δ = i + e - A, A being the angle of the prism.
A = 74°
μmax = sin((A + δ)/2) / sin(A/2)
Putting the values in the above equation, we get μmax = 1.44. The closest option is 1.5