PYQ NEET- The Mirror Equation; Ray Optics

Question 1:

A ray of light travelling in air is incident on a glass slab at an angle of incidence of 30°. The ray does not undergo total internal reflection at the glass-air interface. The critical angle for the glass-air interface is:

The answer is: 45°

The critical angle for a pair of media is the angle of incidence in the first medium for which the angle of refraction in the second medium is 90°.

In this case, the first medium is air and the second medium is glass. The angle of incidence in the air is 30° and the angle of refraction in the glass is 60°. So, the critical angle for the glass-air interface is 45°.

Question 2:

A ray of light is incident at an angle of 60° on a prism of angle 45°. The emergent ray makes an angle of 30° with the incident ray. The refractive index of the prism is:

The answer is: √2

The refractive index of a prism is not given by a single formula but depends on the material and wavelength of light.

n = sin(A + D)/sin(A)