Monday, 25 February 2013

Reflection 1 - Plane Mirrors

This experiment seeks to demonstrate the law of reflection - the angle of incidence is equal to the angle of reflection when measured from the normal.

Equipment

Single slit raybox with power supply
Paper
Ruler
Protractor
Sharp Pencil
Plane mirror
Support for mirror (e.g. wooden block with a groove in, or plasticine)

Method

Draw a line on the paper. Place the mirror on the line and support it so it does not move.
Shine the beam from the raybox towards the mirror. Use the pencil to carefully mark two dots in the centre of the incident and reflected rays.
Move the mirror to one side and use the ruler to join the dots to show the complete path of the ray. Add arrows so you know which direction the ray travelled.
At the point where the ray reflects from the mirror add a line perpendicular to the mirrors surface - this is the normal line.
Use the protractor measure the angle between the normal and the incident ray, and the normal and the reflected ray.

Note these angles in a table and then repeat the experiment for at least three more different angles.

Care should be taken when moving the raybox as those which use an incandescent bulb can get hot to the touch.

Results

You should find that the results show that the incident angle and reflected angle are equal. Your results may be a little out, due to errors introduced with how carefully you marked the path, the normal and measured the angle.