Maharashtra State BoardSSC (English Medium) 6th Standard
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A wave is a disturbance produced in a medium as the particles of the medium vibrate.

The particles produce motion in each other without moving forward or backwards.

This leads to the propagation of sound.

Hence sound is often called a Wave.

How can sound travel through air?

When an object vibrates in the air or produces a sound, some regions of high pressure are created in front of it. These are called the Regions of Compression.

These regions of compression move forward in the medium as particles exert pressure on their adjacent particles.

With alternate regions of compression, there are also regions of low pressure that are in its front. These are called Regions of Rarefaction.

As the object would move forwards and backwards consecutively producing sound, the series of compressions and rarefactions will be created. This will allow sound to move through air or any other medium as well.

If the medium is dense the pressure exerted on the particles will be more in order to propagate the sound and vice versa.

Therefore, we can also say that propagation of sound is all about change in the pressure of the medium.

A wave that is produced when objects of the medium oscillate is called Mechanical Wave. The sound waves are therefore, mechanical waves.

Sound cannot travel through the vacuum as it always needs a medium to propagate. The vacuum contains no air hence no particles can propagate sound.

Longitudinal waves - Any wave that vibrates in the direction of the motion is called a Longitudinal Wave. Sound waves are longitudinal because the particles of the medium vibrate in the direction which is parallel to the direction of the propagation of the sound waves.The particles in the medium oscillate to and fro in the case of longitudinal waves.

Transverse Waves - A transverse wave is produced when the particles of the medium oscillate in a direction which is perpendicular to the direction of the propagation of the wave. The particles in a transverse wave oscillate in an up and down motion. For Example, light waves are transverse in nature.


  • Sound
  • Types of Sound
  1. Longitudinal wave
  2. Transverse wave
  • Categories of sound waves based on their frequencies
  1. Audible waves
  2. Infrasonic waves
  3. Ultrasonic waves
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Video Tutorials

We have provided more than 1 series of video tutorials for some topics to help you get a better understanding of the topic.

Series 1

Series 2 | Longitudinal nature of sound

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Longitudinal nature of sound [00:06:23]
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