Question

A disc is placed on a surface of pond which has
refractive index 5/3. A source of light is placed 4 m
below the surface of liquid. The minimum radius of
disc such that light is not coming out is
(1) 5 m
(2) 3 m
(3) 6m
(4) 4 m

Answer 1

YOUR ANSWER IS IN THE ATTACHMENT PLZZ REFER TO THE ATTACHMENT

Answer 2

Answer:

$given \: refractive \: \: index \: = \frac{5}{3} \: \\ distnce \: = 4m \:$

so with the help of pythagoras theorem ,

=3 m