Object : To verify the laws of Reflection of sound .
Apparatus : Two metallic or cardboard tubes , stopwatch, Drawing board , plastic screen , protractor , chalk piece and a pencil.
Theory : When sound is incident on wood , brick or a plaster wall , it returns back. The returning back of sound after striking a hard surface is called reflection of sound. Sound waves obey the laws of Reflection which are as follows :
1. The angle of incidence is equal to the angle of reflection.
2. Incident wave , reflected wave and the normal lie in the same plane.
Diagram :
Observations:
Result :
1. Angle of incident sound wave = Angle of reflected sound wave.
2. Sound wave , normal and the reflected sound all lie in same plane.
Precautions:
1. Careful measurement of angle should be done by using protractor.
2. Table top should be horizontal and the wooden board should be vertically placed.
3. The stopwatch should be placed near the end of tube placed on the left-hand side.
4. The ear should be placed near the end of the 2nd tube.
5. The tubes should be sufficiently long.
6. The incident sound must be clear and smooth.
Sources of Error :
1. The pipe used in the experiment may not be of larger length.
2. Protractor may not be big enough to measure large angles.