Concepts

Class 9
Chapter 12 Class 9 - Sound

## What are longitudinal waves

In this case, Individual particles of wave move in direction of propagation of waves

In easy language, particles of medium move back and forth (left and right) making nearby particles of medium vibrate

Example

If we stretch a slinky, it moves left and right (in the direction we put force)

## What are Transverse Waves

In this case, particles of medium oscillate up and down at right angles to the direction in which the wave is moving.

Example

If we move a slinky up and down, the wave moves to the right side but slinky moves up and down (right angle to direction of wave

See this image

In the top wave, particles move perpendicular to direction of wave. So, it is a transverse wave

In bottom wave, particles move parallel to direction of wave. So, it is a longitudinal wave

Another example can be

## Are sound waves Longitudinal or Transverse ?

Sound waves are longitudinal waves

It is because sound waves move in back and forth direction

Explanation

When an object vibrates, it forces the particles of medium around it to also vibrate (move to and fro)

They cause the neighbouring particles to vibrate and so on

This process continues until the vibrations reach the person's ear and we are able to hear sound

## Questions

NCERT Question 4 - Why is sound wave called a longitudinal wave?

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#### Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo