HC Verma Chapter 18 Problem 2 – Critical angle for glass-air

Given

Glass n=1.5 to air

Find

Critical angle C

Formula

sin C = 1/n

Solution

sin C = 1/1.5 = 0.6667; C = 41.8 deg

Answer

C = 41.8 deg

Diagram / Concept

Beyond C, total internal reflection occurs

Notes

Critical angle depends only on ratio n2/n1