In Fig. 3.1, the lines AB and CD are mirrors. A student traces a light ray that is reflected by both mirrors. Two optics pins, $P_1$ and $P_2$, are set on the ray that strikes mirror AB. Two further optics pins, $P_3$ and $P_4$, are set on the ray after it has been reflected by mirror CD.
(a(i))[1]
On Fig. 3.1, use the positions of pins $P_1$, $P_2$, $P_3$ and $P_4$ to draw lines showing the ray's route through the mirror arrangement.
(a(ii))[2]
Describe the procedure you followed to draw these lines.
(a(iii))[1]
State a precaution that you used to make sure the lines are drawn accurately.
(b)[3]
The ray meets mirror AB at Q. On Fig. 3.1, (i) label Q, (ii) draw the normal at Q, (iii) measure the angle of incidence $i$ at Q, (iv) measure the angle of reflection $r$ at Q.
(c)[1]
Explain how the student could improve the positions of $P_3$ and $P_4$ to obtain a more accurate value for the angle $r$.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A line through each pair of dots to the mirror, then a joining line between the mirrors” …