Question

The critical angle for glass-air is ${45}^0$ for the light of yellow colour. State whether it will be less than, equal to, or more than ${45}^0$ for (i) red light, (ii) blue light?

Answer 1

As the wavelength decreases (or increases) refractive index becomes more (or less) and critical angle becomes less (or more)

(i) For red light the critical angle will be more than ${45}^0$ and

(ii) For blue light the critical angle will be less than ${45}^0$.