Question

Figures 9.34(a) and (b) show refraction of a ray in air incident at 60° with the normal to a glass-air and water-air interface, respectively. Predict the angle of refraction in glass when the angle of incidence in water is 45º with the normal to a water-glass interface [Fig. 9.34(c)].

Answer 1

As per the given figure, for the glass − air interface: 

Angle of incidence, i = 60° 

Angle of refraction, r = 35° 

The relative refractive index of glass with respect to air is given by Snell’s law as:

As per the given figure, for the air − water interface:

Angle of incidence, i = 60° 

Angle of refraction, r = 47°

 The relative refractive index of water with respect to air is given by Snell’s law as:

Using (1) and (2), the relative refractive index of glass with respect to water can be obtained as:

The following figure shows the situation involving the glass − water interface.

Hence, the angle of refraction at the water − glass interface is 38.68°.