Question

A point source of light is placed 4m below the surface of water of refractive index 5/3. the minimum diameter of a disc, which should be placed over the source, on the surface of water to cut-off all light coming out of water is

Answer 1

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Answer 2

Answer:

The diameter of a disc is 6 m.

Explanation:

Given that,

Height h = 4 m

Refractive index $n=\dfrac{5}{3}$

The diameter of a disc is

$d = 2r$

The radius of the disc is given by

$r= \dfrac{h}{\sqrt{n^2-1}}$

Here, h = height

n = refractive index

$r=\dfrac{4}{\sqrt{(\dfrac{5}{3})^2-1}}$

$r=3\ m$

$d= 6\ m$

Hence, The diameter of a disc is 6 m.