Question

The diagram alongside shows the refraction of a ray of light from air to a liquid.

(a) Write the values of (i) angle ofincidence, and (ii) angle of refraction.

(b) Use Snell's law to find the refractive index of liquid with respect to air.

Answer 1

(a)
(i) Angle of incidence is the angle which the incident ray makes with the normal.
$\angle$ i = ${90}^{\circ }$ - ${30}^{\circ }$ = ${60}^{\circ }$

(ii) Angle of reflection is the angle which the refracted ray makes with the normal.
$\angle$ i = ${90}^{\circ }$ - ${45}^{\circ }$ = ${45}^{\circ }$

(b) According to Snell's law

$\mu$ = $\frac{\sin i}{\sin r}$ = $\frac{\sin 60}{\sin 40}$ = (√3/2)/(1/√2) = √3/2 = 1.22