The thin prism having refracting angle 10^ is made of glass of refractive index 1.42 . This prism is combined with another thin prism of glass of refractive index 1.7 . This combination produces dispersion without deviation. The refracting angle of the second prism is

Step-by-step solution

For a thin prism, the deviation produced is given by = ( - 1)A . For the combination to produce dispersion without deviation, the net deviation must be zero. This means the deviations produced by the two prisms must be equal in magnitude and opposite in direction. ( ₁ - 1)A₁ = ( ₂ - 1)A₂ Substituting the given values: (1.42 - 1) 10^ = (1.7 - 1) A₂ 0.42 10^ = 0.7 A₂ 4.2^ = 0.7 A₂ A₂ = 4.2^ 0.7 = 6^ Answer: 6^