A glass prism of refractive index 1.5 is immersed in water (refractive index 4/3). A light beam incident normally on the face AB is totally reflected to reach on the face BC if.

Options

A. `sintheta gt 8 //9`
B. `sintheta lt 2//3`
C. `2//3 lt sintheta lt 8//9`
D. none

Answer

A

Explanation

Critical angle from glass to water
`mu_gsinC=mu_omegasin90^@`
`3/2sinC=4/3xx1impliessinC=8/9`
T.I.R. takes place on AC i.e.
`thetagtC`
`sinthetagtsinC`
`sinthetagt8//9`