Question 1 Define sound?

Question 2 What type of wave are sound wave in air?

Question 3 Name two types of sound waves which are generated in a long spring?

Question 4 What are mechanical waves?

Question 5 Explain the term compression?

Question 6 Explain the term rarefaction?


Sound is a form of energy .It is that form of energy which makes us hear.

Production of Sound

Sound can be produced by striking,plucking,scratching,rubbing,blowing or shaking different objects.
Vibration is a kind of rapid to and fro motion of an object.
The sound of the human voice is produced due to vibration in the vocal cords.

Propagation of Sound
The matter or substance through which sound is transmitted is called medium(solid,liquid or gas).

Sound moves through a medium from point of generation to the listener.
When an object vibrates,it sets the particles of medium around it vibrating.The particles do not travel all the way from the vibrating object to the ear.

A particle of medium in contact with vibrating object is first displaced from its equilibrium position.It then exerted a force on adjacent particle.As a result of which the adjacent particle gets displaced from its position of rest.

After displacing the adjacent particle the first particle comes back to its original position.The process continues in the medium till the sound reaches your ear.

The disturbance created by a source of sound in the medium travels through medium and not the particle in the medium.

A wave is a disturbance in a medium which carries particle or energy from one point to another without there being a direct contact between the two points.

When a wave passes through a medium,the medium itself does not move along the direction of the wave,only the particles of the medium vibrate about their fixed position.

Sound can be visualised as a wave.Sound wave are characterised by the motion of particle in the medium and are called mechanical waves.

Air is the most common medium through which sound waves travel.

Sound wave are longitudinal waves(A wave in which the particles of medium vibrate back and forth in the same direction in which the wave is moving)
The direction of vibration of particle is parallel to direction of wave.

When the vibrating particle come closer to one another than they normally are,then there is a reduction in volume and compression is formed.

When the vibrating particle move farther apart from one another than they normally are,there is an increase in volume and rarefaction is formed.

When a vibrating object moves forward,it pushes and compresses the air in front of it creating a region of high pressure(compression).

When a vibrating object moves backward,it creates a region of low pressure(rarefaction).

As the object moves back and forth rapidly,a series of compression and rarefaction are formed in air.These make the sound wave to propagate through the medium.
Pressure is related to number of particles of a medium in a given volume.Sound wave cannot travel through vacuum.

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