55. A thin prism of angle 15° made of glass of refractive index $μ_1$ = 1.5 is combined with another prism of glass of refractive index $μ_2$ = 1.75. The combination of the prism produces dispersion without deviation. The angle of the second prism should be ?

54. The refractive index of the material of a prism is √2 and its refracting angle is 30°. One of the refracting surfaces of the prism is made a mirror inwards. A beam of monochromatic light enters the prism from the mirror surface if its angle of incidence of the prism is ?

53. The refractive index of the material of the prism is √ 3; then the angle of minimum deviation of the prism is ?

52. Angle of deviation ( δ ) by a prism (refractive index = μ and supposing the angle of prism A to be small) can be given by ?