A point source S is placed at the bottom of a tranparent block of height 10mm and refractive index 2.72. It is immersed in a lower refractive index liquid as shown in the figure. It is found that the light emerging from the block to the liquid forms a circular bright spot of diameter 11.54 mm on the top of the block. The refractive index of the liquid is `

Options

A. 1.21
B. 1.3
C. 1.36
D. 1.42

Answer

C

Explanation

Applying Snell's law at point P
`n_(1)sintheta=n_(2)sin90degree`
`:'` `n_(2)=2.72xx((11.54)/(2))/(sqrt((10)^(2)+((11.54)/(2))^(2)))`
`:'` `n_(2)=1.36`