Question

1. Describe resonance. Give at least two examples and be sure that you identify the source and the receiver.
2. Give two examples which will demonstrate that the speed of sound depends on the density of the particles of the medium and on medium elasticity.

Answer 1

Solution : resonance is a condition in which the natural frequency of vibration of an object matches the frequency of the driving force. Due to this the amplitude of vibration gets double and we hear a more intense sound. The phenomena only occur at some special frequencies.

Example :1 the resonance tube in which water is filled and the tuning forks are used to create resonance condition. The experiment is used to find the speed of sound in air.

2. Resonance is cause of production of sound in musical instruments . When a wind pipe is blown then at some certain lengths of wind pipe different sounds are heard . You may have seen various holes on the wind pipe. These holes are used to change the length of wind pipe for different sounds. When we blow air we create vibrations in the Pipe if this vibration matches the natural frequency of selected length we get strong sound.

2. The speed of the sound is dependent on elasticity and density of medium. The most common example which I suggest my students to compare the speed of sound is in air and hydrogen gas.

The sound travel faster in Hydrogen gas as it has less density than air. So here density of medium affects the speed.

2. Similar example is speed of sound in air and iron . The elasticity of iron is very high hence speed of sound is large in iron as compared to air.

For this if a train is moving on a track we can hear the sound of the train from a very large distance if we put our ear near the railway track which is made up of iron, however if you just stand near by the track you do not hear any sound.