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.
Hypothesis – The angle of reflection will always be the same as the angle of incidence.
Apparatus and Materials – * Mirror * Light Box * Power Pack * Paper * Ruler * Protractor * Pencil Safety –
- Be careful not to touch the light box as it will be hot.
- Don’t put the voltage above 12.
Method – 1. Set up the Power pack by plugging it into the wall. 2. Plug the light box into the power pack using the yellow sockets 3. Slide the black insert into the end of the power pack so that the single slit end is at the bottom and one beam of light is shining out. (The end closest to the lightbulb) 4. Place a blank piece of paper underneath the light box and place the mirror about 10 cm away from it. 5. Draw a line down the side of the mirror to show where the angles will be measured from. 6. Now draw the ‘normal’ onto the line of the mirror. 7. Now place the paper back where it was before and put the mirror back on the line. 8. Set the paper in a position so that you get the beam of light reflecting off the mirror and back onto the paper . 9. Draw down the centre of the beam of light on both the reflection and the original beam. Make sure that the point where the lines are drawn is the same as the point of the normal. 10. Now remove the paper and using the protractor measure the angle of the line from the normal on both sides of the mirror line. The one where the original beam meets the mirror is the angle of incidence and the one where it is reflected is the angle of reflection. 11. Record the results. 12. Repeat steps 8-12 four times.
Variables –
Independent – Angle of Incidence
Dependant – Angle of Reflection
Controlled – How far the paper is from the light (The width of the beam).
- The mirror
