Experiment for Laws of Reflection
For the experiment we need the following items:
- White sheet of paper
- A comb
- A sheet of black paper
- Torchlight
- Plane mirror
Cover all the openings of the comb except the middle one with the black sheet of paper. Place the comb perpendicular to the paper as shown below.
Now, light up a torch. Throw its light through the opening of the comb from one side. Adjust the torch to see the light on the paper. When a plane mirror is placed in the light’s path, the reflection of light can be seen on the paper. These are the incident ray and reflected ray.
When the incident ray and reflected ray are represented on the paper, the diagram will look as shown below. Also note that a normal is drawn, perpendicular to the mirror surface. The angles formed by the incident ray and the reflected ray with the normal are the angle of incidence ‘i’ and the angle of reflection ‘r’ respectively.
If ‘i’ and ‘r’ are measured with a protractor, they will be approximately equal. If the angle of incidence is increased by moving the comb slightly, the angle of reflection also increases. In this case as well, the angles will be almost equal.
But the first law of reflection states that the angle of incidence is equal to the angle of reflection. The discrepancy we see in the reading is due to errors during measurement. Also, the accuracy of the angle depends on the narrowness of the light beam. Narrower the beam, more accurate will be the results.
It is important to note that a beam of light is different from a ray of light and in this experiment, the light is a beam of light. A ray of light is simply an idealisation of a beam. A beam is visible, but a ray of light is not. But as of now for our understanding, think of the narrow beam of light as a ray of light.
Summary
| Laws of
Reflection |
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Did you know?
Light is made up of little packets of energy called photons. They are produced when the atoms in an object heat up. Heat “excites” the electrons inside the atoms and they gain extra energy.
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