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 surface, the radius of this circle is cm is

Options

A. `36 sqrt(5)`
B. `4 sqrt(5)`
C. `36 sqrt(7)`
D. `36 // sqrt(7)`

Answer

D

Explanation

`sin i_(c ) = = (R )/(sqrt( R^(2) + h^(2)) )`
`rArr " " ((3)/(4))^(2) = (R^(2)) /(R^(2) + (12)^(2))`
`rArr " " R = (3)/(sqrt(7)) xx 12 = (36)/(sqrt(7)) ` cm .