A beam of monochromatic light is incident at i = 50° on one face of an equilateral prism, the angle of emergence is 40°, then the angle of minimum deviation is :
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Question

A beam of monochromatic light is incident at i = 50° on one face of an equilateral prism, the angle of emergence is 40°, then the angle of minimum deviation is :

G1 Physics · Accepted Answer

Derived solution: Step 1: For a prism use r₁ + r₂ = A and δ = i + e - A. At minimum deviation i = e and r₁ = r₂ = A/2, so μ = sin[(A + δₘ)/2]/sin(A/2). Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is < 30°. Therefore the correct option is B.