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A point source of light is placed 4 cm b...

A point source of light is placed 4 cm 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

A

infnite

B

6 cm

C

4 cm

D

3 cm

Text Solution

Verified by Experts

`r=(h)/(sqrt(mu^(2)-1))=(4)/(sqrt(((5)/3)^(2))-1)=3m` , Diameter = 2r = 6m
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