A plane polarized blue light ray is incident on a prism such that there is no reflection from the surface of the prism. The angle of deviation of the emergent ray is δ = 60 o (see Figure- 1 ). The angle of minimum deviation for red light from the same prism is δ min = 30 o (see Figure- 2 ). The refractive index of the prism material for blue light is 3 . Which of the following statement(s) is(are) correct?
D. The angle of refraction for blue light in air at the exit plane of the prism is 60 o
For no reflection: tan i = 3 ⇒ i = 60 ° Applying Snell's law at left interface, we get ⇒ 1 × sin i = 3 × sin r 1 ⇒ sin r 1 = 1 2 ⇒ r 1 = 30 o Now, for given values δ = i + e - A ⇒ 60 ° = 60 ° + e - A ⇒ e = A Then, A = r 1 + r 2 ⇒ r 2 = A - r 1 = 30 o For red light: Expression to find minimum deviation is given by, μ = sin A + δ m 2 sin A 2 = sin 60 ° + 30 ° 2 sin 60 ° 2 = 1 2 1 2 = 2
Related: Physics — Ray Optics · All PYQ Banks