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 ]

Question

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 ], 50 %, 25 %, 20 %, 17 %

MARKS App · Accepted Answer

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 r escaped energy total energy = 0.17 total % energy enscaped = 17 %

Search any question & find its solution

Looking for more such questions to practice?