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A light ray is incident on an equilateral prism in such a way that the angle of incidence equals the angle of emergence, and this common angle is three-fourths of the prism angle. What is the angle of deviation produced?

1. 25°
2. 30°
3. 45°
4. 35°

Correct answer: 30°

Solution

Equilateral prism A=60 deg, i=e=(3/4)(60)=45 deg. Deviation delta = i + e - A = 45 + 45 - 60 = 30 deg.

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