You will investigate the light reflected from a plane mirror. You are provided with: • a plane mirror in a holder • a slit cut into card and a lamp to illuminate it, or a ray box and a single slit • a protractor • a 30 cm ruler.

1. (a)Fig. 2.1 shows a straight line AB. [Figure 2.1]
2. (a)(i)Draw a line from point A at an angle of 30° in an anticlockwise direction from AB. This line should be more than 10cm long. Label the end of the line as point C.[1]
3. (a)(ii)Mark a point D on the line AB, 4.0 cm from point A. Draw a line perpendicular to AB through point D. This line must also pass through the line AC that you have drawn in part (a)(i). Label, with an E, the point where the line through point D passes through AC.[1]
4. (b)(i)Place the front surface of the mirror along the line AC on Fig. 2.1 with the reflective surface facing point B. Using the illuminated slit, pass a ray of light along the line DE towards the mirror. The ray should reflect from the mirror. Mark with crosses (X) two points on the reflected ray. Label these points P₁ and P₂.[1]
5. (b)(ii)Remove the mirror. Draw a line through points P₁ and P₂ and extend it to meet line AC. This is the reflection of the line DE.[1]
6. (b)(iii)Describe how points P₁ and P₂ are chosen to give as accurate a reflected line as possible.[1]
7. (b)(iv)Label the angle between CE and EP₁ as θ. Measure and record angle θ. θ = _______ °[1]
8. (c)(i)Fig. 2.2 shows a second line labelled A'B'. [Figure 2.2] On Fig. 2.2, draw a line from point A' at an angle of 60° in an anticlockwise direction from line A'B'. This line should be more than 10cm long. Label the end of the line with a C'. Mark a point D' on the line A'B', 4.0cm from point A'. Draw a line perpendicular to A'B' through point D'. This line must also pass through the line A'C' that you have drawn. Label the point where the line through point D' passes through A'C' with an E'. Place the front surface of the mirror along the line A'C' on Fig. 2.1, with the reflective surface facing point B'. Using the illuminated slit, pass a ray of light along the line D'E' towards the mirror. The ray should reflect from the mirror. Mark with crosses (X) two points on the reflected ray. Label these points P₃ and P₄. Remove the mirror. Draw a line through points P₃ and P₄ and extend it to meet line A'C'. This is the reflection of the line D'E'.[1]
9. (c)(ii)Label the angle between C'E' and E'P₃ on Fig. 2.2 as α. Measure and record angle α. α = _______ °[1]
10. (c)(iii)Assume that the line E'P₃ has been drawn accurately. State one practical precaution, other than your answer to (b)(iii), that you take to ensure that the drawn angle α can be measured accurately.[1]
11. (d)Theory suggests that: θ = 2α where θ is the answer to (b)(iv) and α is the answer to (c)(ii). State whether your results support this theory. Give a reason for your answer.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.