Study Hack Lab

RP 9Physics

Light

Write-up template

Name
Date
Course: GCSE Physics
Board and specification: AQA GCSE Physics (8463), 4.6.1.3Apparatus and techniques: AT 4, AT 8
Class and teacher

Aim

Investigate the reflection of light by a plane mirror and the refraction of light by glass and Perspex blocks.

Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up

A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.

1 Plan and risk assessment

A smooth surface reflects light at the same angle it arrives at, measured from the normal (a line at 90° to the surface). When light goes from air into glass or Perspex it slows down, so it bends towards the normal: the angle of refraction is smaller than the angle of incidence.

angle of incidence = angle of reflection

Variables

Independent (you change)
Dependent (you measure)
Control (you keep the same)

Prediction

You shine a ray at the mirror along the 30° line (30° from the normal). What will the angle of reflection be?

What will the ray do as it goes from the air into the glass block (not along the normal)?

Glass and Perspex are both clear blocks. Will your protractor show that they bend light by different amounts?

Risk assessment

Hazard	Harm it could cause	Control

2 Apparatus

Ray box with a single-slit card and lens, and a 12 V power supply Makes a narrow ray of light.
Sheet of plain A3 paper and tape You draw the lines and mark the rays on it.
Sharp pencil Draws thin, exact lines and crosses.
30 cm ruler (resolution 1 mm) Draws the surface line and joins the crosses.
Protractor (180°) (resolution 1°) Draws the normal and the incident lines, and measures the angles.
Plane mirror in a holder Reflects the ray (specular reflection).
Rectangular glass block Refracts the ray.
Rectangular Perspex block, the same size Refracts the ray: compared with glass.

3 Method

Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.

4 Results

The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.

Plane mirror · Move the ray box away and put it back on the line before each trial.

Trial	Angle of reflection (i = 30°) in degrees	Angle of reflection (i = 60°) in degrees
1
2
3
Mean

Glass and Perspex blocks · Angles measured from the normal.

Angle of incidence in degrees	Angle of refraction (glass) in degrees	Angle of refraction (Perspex) in degrees
10
20
30
40
50
60
70

Anomalies

Ring any anomalous result. Say what probably went wrong and whether you repeated it.

5 Graph

Recorded angle against angle of incidence (glass) · Choose your axes: the independent variable goes on the x-axis. Label each axis with the quantity and unit.

6 Analysis

Uncertainty in the mean
uncertainty = range ÷ 2
Answer

7 Conclusion and evaluation

Conclusion

Conclusion: what do your results show? Use your own numbers.

Sources of error

For each, say whether it is systematic or random, and how it affected your results.

Judging where the centre of the ray is when you mark each cross

Crosses close together on the ray

Normal drawn by eye, not at 90° to the surface

Measuring the angles from the surface instead of the normal

Not putting the ray box or the block back in exactly the same place

Resolution of the protractor (1°)

Improvement

How could you improve the method? Say why it would help.

8 Make safe and clear up

Switch off the ray box and switch the room lights back on
Leave the ray box to cool, then move it by its base
Put the glass and Perspex blocks back in their padded box, and the mirror in its holder
Label each part of your traced sheet (mirror, glass, Perspex) and keep it with your results