question_answer

A fish looking up through the water sees the outside world, contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the water surface, the radius of this circle (in cm) is    [AIEEE 2005]

A) \[36\sqrt{7}\]

B) \[\frac{36}{\sqrt{7}}\]

C) \[36\sqrt{5}\]

D) \[4\sqrt{5}\]

Correct Answer: B

Solution :

[b] The situation is shown in figure.

By Snell's law,

where,is critical angle,

or