6E-WS7
THE LAW OF REFLECTION
Aim: To be able to correctly set up apparatus and accurately measure the angle of reflection.
Task:
Reflect a light ray off a
plane mirror and compare
the angle of incidence with
the angle of reflection.
Keywords:
Plane mirror -
A flat mirror, drawn as a straight line with dashes underneath.
Normal -
An imaginary line that is draw straight up from where the light ray
hits the mirror.
Angle of incidence - The angle between the normal and the incident light ray.
Angle of reflection - The angle between the normal and the reflected light ray.
Equipment:
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Plane mirror
light ray box with single slit
pencil, ruler and protractor
Plain white paper
Method:
1. Collect your equipment and set it up so that the single slit is in front of the light ray box and
produces a single thin light ray.
2. Place the mirror on its side and angle the beam so that it reflects off the mirror. Make sure that the
end of the light ray box is also on the paper.
3. Using a pencil place a single dot where the light ray leaves the light ray box, a dot where it hits the
mirror and finally a dot about 10cm on along the reflected light ray.
4. Being careful not to move the mirror, draw a line using a pencil along the surface of the mirror.
5. Join up the dots in the order you placed them and draw in the normal, using a ruler, as a dotted
line.
6. Using a protractor, measure the angle between the incident ray and the normal and the reflected
ray and the normal, these will be the angle of incidence and the angle of reflection respectfully.
7. Repeat for different angles.
6E-WS7
THE LAW OF REFLECTION
Results:
Conclusion:
What have you found out from this investigation?
θi
θr
.................................................................................................
.................................................................................................
.................................................................................................
Were any angles of incidence different from the correlating
angle of reflection? If so why do you think this was the case?
.................................................................................................
.................................................................................................
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Draw a perfect light ray diagram where θi = 45° and θr = 45°
THE LAW OF REFLECTION!!
The angle of reflection is ..................... the
.................... as the angle of incidence.