(a(i))[1]
On Fig. 2.1, mark $P$ and label it as the mid-point of side $AB$ of the prism.
(a(ii))[1]
On Fig. 2.1, draw the normal at $P$ to the prism.
(a(iii))[1]
On Fig. 2.1, draw a line to show a ray of light incident at $P$ with an angle of incidence of $40^{\circ}$.
(b)[4]
Describe how the student can use the narrow beam of light to determine the path of the ray through the prism.