A thin prism P₁ with an angle 6° and made of glass of refractive index 1.54 is combined with another prism P₂ made from glass of refractive index 1.72 to produce dispersion without average deviation. The angle of prism P₂ is:
Options

Question

A thin prism P₁ with an angle 6° and made of glass of refractive index 1.54 is combined with another prism P₂ made from glass of refractive index 1.72 to produce dispersion without average deviation. The angle of prism P₂ is:

Options

G1 Physics · Accepted Answer

For zero average deviation, (n₁−1)A₁ = (n₂−1)A₂. Thus (1.54−1)×6° = (1.72−1)A₂. Hence A₂ = 6×0.54/0.72 = 4.5°.