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In an experiment for determination of refractive index of a prism by i − δ, plot 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. 1.7
2. 1.8
3. 1.5
4. 1.6

Correct answer: 1.5

Solution

From delta = i + e - A, the prism angle A = 35 + 79 - 40 = 74 deg. Working through the refraction at the faces, the largest consistent refractive index is about 1.5 (JEE Main 2016).

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