A point source of light is placed at a distance h below the surface of a large deep lake. Neglecting the partial reflection of light during refraction, the percentage of light energy that escapes from the water surface is [ μ water = 4 3 ]

Step-by-step solution

Solid angle ϕ = 2 π 1 − cos θ where θ = plane angle escape energy = total energy 4 π × solid angle escape energy total energy = 1 4 π × 2 π 1 - cosC = 1 2 1 - cosC           ....(1) from law of refraction μ w sin     i = μ a   sin     r 4 3 × sin C = 1 × sin 90 o sin C = 3 4 ⇒ cos C = 1 - sin 2 C ⇒ cos C = 7 4 .... 2 from (1) and (2) μ w sin   i = μ a sin