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Aim of the experiment

To investigate the reflection of light by a plane mirror.

Method

1. Set up a ray box, slit and lens so that a narrow ray of light is produced.
2. Place a 30 centimetre (cm) ruler near the middle of a piece of plain A3 paper. Draw a straight line parallel to its longer sides. Use a protractor to draw a second line at right angles to this line. Label this line with an 'N' for 'normal'.
3. Place a plane mirror against the first line.
4. Use the ray box to shine a ray of light at the point where the normal meets the mirror. This is the incident ray.
5. The angle between the normal and the incident ray is called the angle of incidence. Move the ray box or paper to change the angle of incidence. The aim is to see a clear ray reflected from the surface of the mirror.
6. Using a pencil on the paper, mark the path of:
   • the incident ray with a cross
   • the reflected ray with a cross
7. Remove the mirror. Join the crosses to show the paths of the light rays.
8. Measure the angle of incidence and angle of reflection for the mirror.
9. Repeat steps 2 - 8 for several different angles of incidence.

Results

Record results in a suitable table.

Analysis

Compare the angle of incidence with the angle of reflection for each block.

Evaluation

The light rays should obey the law of reflection for every attempt. To what extent do the results show this?

Risks/hazards