The law of reflection states that the angle of incidence will be equal to the angle
of reflection. I.e. the angle that the light strikes the reflective surface at will be
the same as the angle that it leaves it at.
To investigate the law of reflection and evaluate its accuracy.
The law of reflection will be correct.
Apparatus and Materials
This experiment is potentially risky. The first risk is that the light box heats up
quite a lot and so there is a danger of burning yourself. It also requires a power
box, which increases the risk of electrocution, although the risk is small. The
second is that this must be done in a dark room which is precautions are not
taken, could be dangerous due to the lack of vision.
Independent Variable: Angle of Incidence
Dependant Variable: Angle of Reflection
Controlled Variables: Mirror location, amount of light
1. Set up light box so that one slit of light escapes from the box. (The light
box must be plugged into the power box, which must be plugged into the
2. Set the protractor with the flat edge against the mirror.
3. Aim the light beam at different intervals on the protractor.
4. Measure the angle of reflection.
No. Angle of Incidence Angle of Reflection
1 20o 20o
2 30o 30o
3 40o 40o
4 50o 50o
5 60o 60o
The angle of reflection is clearly the same as the angle of incidence. This result
occurred in every instance.
By definition, the angle of reflection should equal the angle of incidence, as it is a
reflection-a reversed copy-of the original angle. Therefore, logically the reflected
light should be identical, simply travelling in the reversed direction.
I think that the data collected is fairly reliable. It could be questioned as the
experiment was only repeated once and it was done fairly hastily. However, the
law that the angle of incidence equals the angle of reflection is well tested and
undisputed. As I received results that support the theory, I am inclined to draw
the conclusion that the results are reliable.
A benefit of the experiment is that it is very easy to perform. This means that it
will be quick and accurate. Another benefit is that the results are very
straightforward if the experiment is set up properly. The angles are either the
same or they aren’t.
Despite the simple nature of the experiment, a light box is not readily available to
most. Substitutes can be made but a light box is the most effective way of doing
I thin that this experiment is valid as it demonstrates the law of reflection well.
After doing this experiment, exploring other areas of light would be very useful
and intriguing. Perhaps exploring refraction and its laws would be a good way to
continue my exploration in light.
My results support my hypothesis. The law that the angle of incidence equals the
angle of reflection is correct.