Asked by Abc123736 | 8th Dec, 2015, 09:07: PM

Expert Answer:

Laws of reflection:
The reflection at a surface obeys two laws of reflection:
1. First law of reflection: The incident ray, the normal to the surface at the point of incidence and the reflected ray, all lie in the same plane.
2. Second law of reflection: The angle of incidence is equal to the angle of reflection.
If a light ray is incident normally to the surface, then the angle of incidence and the angle of reflection are zero.
Experimental verification of laws of reflection:


1. A white paper is fixed on a drawing board with line MM′ drawn on it. Draw a point O in the middle and a line OA such that begin mathsize 14px style angle MOA end style < 90°. Now, draw normal ON. Then, set a plane mirror along MM′.

2. Fix two pins P and Q on OA. Now, look from the other side of the normal and see the images P′ and Q′.

3. Fix pins at points R and S in line with the images P′ and Q′ of pins P and Q. Then, draw small circles around the four pins and remove the pins. Draw line OB joining points R and S.

4. The figure below shows the observation of the above arrangement.


5. Measure begin mathsize 14px style angle AON space equals space straight i end style and begin mathsize 14px style angle BON space equals space straight r end style. Record the observations for different directions of incident ray OA.

6. The experiment is performed on a flat drawing board and the tips of the pins lie on the same plane. Thus, the incident ray, normal ray and reflected ray, all lie on the same plane, verifying the first law of reflection.

7. It will also be observed that the angle of incidence is always equal to the angle of reflection. This verifies the second law of reflection.

Answered by Faiza Lambe | 9th Dec, 2015, 12:34: AM