class 9 science chapter sound notes

class 9 science chapter sound notes, cbse class 9 sound chapter notes full explained in detail, science chapter sound class 9 notes write in easy and simple language, any one can understand. here is the collection of topic or covered topic is Mechanical wave and Non mechanical wave or electromagnetic waves, Longitudinal wave and transverse wave Characteristic of sound, Reflection of sound and much more small topic in full explanation in easy language.

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Mechanical wave and Non mechanical wave

Mechanical wave:-

The wave which need a material medium for their propagation are called mechanical wave.
The medium may be solid, liquid or gas.
Mechanical wave propagate through a medium due to the elastic properties of the medium due to this reason mechanical wave are also called elastic wave.
Mechanical waves cannot travels through vaccum.
Mechanical waves may be longitudinal, transverse wave.
Speed of mechanical waves are low and depends upon the source and the medium through which they travels.
Mechanical waves are due to the vibrations of the particles of the medium.
Example of mechanical waves are sound waves and water waves.

Non mechanical wave:-

The wave which do not need any material medium for their propagation of the sound is called non mechanical wave.
Non mechanical wave can also travels through a material medium as well as vaccum.
Electromagnetic waves are also called non mechanical waves.
Light waves are non mechanical waves.
Non mechanical wave can travels through vaccum.

Electromagnetic wave :-

The wave which are associated with oscillating electrical and magnetic field and which do not need any material medium for the propagation of sound are called electromagnetic wave.
electromagnetic wave can even travels through vaccum. ex. light waves, redio waves, television wave and x ray are electromagnetic waves.
Electromagnetic waves are transverse wave.
Electromagnetic waves travels with a speed of 3 х 10˄8 m/s.
The speed of an electromagnetic waves in any material medium is less then that in vaccum.
Sound waves travels with low speed about 344 m/s at 20° C in air.
Light wave and radio wave travels with velocity of light.

Longitudinal wave and Transverse wave

Longitudinal wave:-

In this wave particles of the medium vibrate to and fro about their mean position in the direction of propagation of the wave is called a longitudinal wave.
The wave which travels along a spring when it is pushed and pulled at one end are called longitudinal wave.
Longitudinal wave can be produced in any medium ( like solid, liquid or gas ) . ex:- when a sound wave passes through air the particles of air vibrate back and forth parallel to the direction of sound wave.
When the vibrating particles come closer to one another then their is a movementry reduction in volume and a compression is formed, on the other hand when the vibrating particles apart from one another then they normally their is a movementry increases in volume and a rarefaction is formed.

Experiment to show that how compression and rarefaction is formed in air.

Compression:-

It is the part of a longitudinal wave in which the particles of the medium are closer to one another.

Rarefaction:-

It is the part of a longitudinal wave in which the particles of the medium are further apart from the normal is called rarefaction.

Transverse wave:-

A wave in which the particles of the medium vibrate up and down at right angle to the direction in which the wave is moving is called a transverse wave.

Transverse wave can be produced only in solid and liquid but not in gas.
Example:- when a stone is droped in a pond of water, transverse water waves are produced on the surface of water. even the light wave and radio waves are transverse wave because this wave cannot travels through air we know that transverse wave also cannot consist of medium gases.
A transverse wave travels horizontally in a medium, the particles of the medium vibrate up and down in the vertical direction.
The wave propagates in the form of crest and trough.
These waves can travels through solid and on the surface of liquid only, as the propagation of these waves causes change in the shape of the medium.
As there is no vibration of volume, there is no vibration in the density of the medium while the wave propagates through it.
There is no created in pressure in the medium while the wave propagate.

Transverse wave described Graphically

Crest;-

The point of maximum position displacement on a transverse wave is called a crest.

Trough;-

The point of maximum negative depth displacement on a transverse wave is called trough.

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