Question

The critical angle for glass-air is ${45}^o$ for the light of yellow colour. State whether it will be less than , equal to, or more than ${45}^o$ for red light?

• A. more than ${45}^o$
• B. less than ${45}^o$
• C. same as ${45}^o$
• D. can't say

Answer 1

The correct option is A more than ${45}^o$

According to Snell's Law: $\frac{sin{i}_c}{sinr}=\frac{n_2}{n_1}$ and for critical angle of incidence $r={90}^o$ and $n_2=1$

Red light has lower refractive index than yellow light hence it's critical angle will be higher than yellow light.