A thin prism of angle 15⁰ made of glass of refractive index µ₁ = 1.5 is combined with another prism of glass of refractive index µ₂ = 1.75. The combination of the prism produces dispersion without deviation. The angle of the second prism should be

Options

(a) 7⁰
(b) 10⁰
(c) 12⁰
(d) 5⁰

Correct Answer:

10⁰

Explanation:

Deviation= 0, so ? = ?￢ﾂﾁ + ?￢ﾂﾂ = 0
(µ₁ – 1)A₁ + (µ₂ – 1)A₂ = 0
A₂(1.75 – 1) = – (1.5 – 1) 15⁰
A₂ = – 0.5 / 0.75 x 15⁰
or A₂ = – 10⁰
Negative sign shows that the second prism is inverted with respect to the first.