AQA · GCSE · Physics · Higher

Measuring Refraction Angles Accurately

Q01.2 6 marks

A student investigated the refraction of light by a glass block. Table 1 shows the results.

Table 1

Angle of incidence in degrees	Angle of refraction in degrees
10	6
20	12
30	18
40	23
50	28
60	32

Describe a method the student could have used to obtain the data in Table 1. You may include a labelled diagram.

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Marking points

1 Gives a valid, logically sequenced method capable of producing the data.
2 Places the glass block on paper and records its outline.
3 Shines a ray from a ray box through the glass block and marks the entering and emerging ray paths.
4 Joins the marked points and draws a normal at 90° to the surface.
5 Uses a protractor to measure both the angle of incidence and the angle of refraction.
6 Repeats for a suitable range of incidence angles, consistent with 10° intervals from 10° to 60°.

Full-mark answer

Place the glass block on a sheet of paper and draw around it. Shine a narrow ray from a ray box into the block. Mark points along the ray entering the block and the ray emerging from it, remove the block, and join the points to show the full ray path. At the surface draw a normal at 90° and use a protractor to measure the angle of incidence and the angle of refraction. Repeat with incidence angles from 10° to 60° in 10° steps, recording the refraction angle each time.

Why this answer loses marks

Use a mirror and measure the reflected ray.

The official guidance says a mirror-and-reflection method scores nothing; the ray must pass through the block and both boundary angles must be measured.