A thin prism P₁ with an angle 6^ and made of glass of refractive index 1.54 is combined with another prism P ₂ made from glass of refractive index 1.72 to produce dispersion without average deviation. The angle of prism P ₂ is :

Step-by-step solution

Angle of deviation for first prism ₁=A₁ ( ₁-1 )=6(1.54-1) Angle of deviation for second prism aligned & ₂=A₂ ( ₂-1 ) & =A₂(1.72-1) aligned For dispersion without deviation aligned & ₁= ₂ & 6^ (1.54-1)= A ₂(1.72-1) & A ₂= 6^ 0.54 0.72 = 18^ 4 =4.5^ aligned