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A small angled prism of refractive index 1.6 gives a deviation of 3.6°. The angle of the prism is ______.

Asked in GUJCET 2018 · Deviation and minimum deviation

Answer: (2) 6°

Step-by-step solution

Given: refractive index n=1.6, deviation δ=3.6°, and the prism angle is small.

Idea: for a thin prism the deviation is δ=(n-1)A, the same for every angle of incidence, so no minimum-deviation condition is needed.

Rearranging, A=δ/(n-1)=(3.6°)/(1.6-1)=(3.6°)/(0.6).

So the angle of the prism is A=6°, which is indeed small enough for the thin-prism formula to hold.

Why the other options are wrong

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