A point source of light is kept below the surface of water `(n_(w) = (4)/(3))` at a depth of `sqrt7` m . The radius of the circular bright patch of light noticed on the surface of water is …… m .

Options

A. `(3)/(sqrt7)`
B. 3
C. `(sqrt7)/(3)`
D. `sqrt7`

Answer

B

Explanation

Here , Refractive index of water , `n_(w) = (4)/(3)`
`sin C = (1)/(n_(w)) = (1)/((4)/(3)) = (3)/(4)`
`tan C = (3)/(sqrt7) " " … (i)`

`tan C = (R)/(sqrt7) " " …. (ii)`
Equating (i) and (ii) , we get `(3)/(sqrt7) = (R)/(sqrt7)` or R = 3 cm