In the figure below, a ray of light A incident from air suffers partial reflection and refraction at the boundary of water.

(a) Complete the diagram showing (i) the reflected ray B and (ii) the refracted ray C.

(b) How are the angles of incidence i and refraction r related?

(a) Below is the completed diagram with the refracted ray B and the reflected ray C labelled:

(b) The relation between angle of incidence i and the angle of refraction r is given by Snell’s law as,

The ratio of the sine of the angle of incidence i to the sine of the angle of refraction r is constant for the pair of given media.

$\dfrac{\text{Sin i}}{\text{sin r}} = \text {constant }$1\mu2 \\[0.5em]

The constant ₁μ₂ is called the refractive index of the second medium with respect to the first medium

$\dfrac{\text{sin i}}{\text{sin r}} = \mu w$