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 45 � with the normal to a water-glass interface [Fig. 9.34(c)].

For the glass -air interface:

Angle of incidence, i = 60^°

Angle of refraction, r = 35^°

According to Snell’s law,

⇒

⇒

⇒

Note: refractive index is a unitless quantity.

For the water -air interface:

Angle of incidence, i = 60^°

Angle of refraction, r = 47^°

According to Snell’s law,

⇒

⇒

⇒

⇒

For the glass - water interface:

Angle of incidence, i = 45⁰

Angle of refraction, r = ? ⁰

According to Snell’s law,

⇒

⇒

⇒ r ≈ 37^°

Therefore, the angle of refraction in glass is