PQR is a right angled prism with other angles as `60^(@)` and `30^(@)` . Refractive index of prism is 1.5. PQ has a thin layer of liquid. Light falls normally on the face PR. For total internal reflection, maximum refractive index of liquid is

Options

A. 1.4
B. 1.3
C. 1.2
D. 1.6

Answer

B

Explanation

For TIR at PQ :
`theta ge i_(c ) rArr 60 gt i_(c ) " " [ because theta 60^(@) ]`
`rArr " " (sqrt(3))/(2) gt (n_(l))/(n_(p)) " " rArr n_(l) lt (sqrt(3))/(2) xx n_(p)`
`rArr " " n_(l) lt (sqrt(3))/(2) xx 1.5 " " rArr n_(l) lt 1.3` .