This article is written for the Tnpsc exam for the topic ‘Sound’, in General studies. Science part (Physics).
This note is for quick revision purposes only, Kindly refer to Samacheer Kalvi Book.
What is sound in physics?
Sound is a type of energy that creates a sensation in our ears. Sound in physics is the vibration of objects or substances. These vibrations travel as a form of disturbances or waves using a medium such as air, water, railway track etc. and reach our ear as sound.
Not all the sounds humans can hear. Humans can sound of certain ranges. Not all sound is as pleasant as music. Some sounds are noises that are unpleasant to hear.
Production of Sound can be observed everywhere, some practical examples of sound production in the lab using Tuning Fork. Tuning Fork produces sound when vibrates. Tumbler with water, when hit by spoon, produces sound also vibration in water is noticed.
Here mechanical energy vibrates the objects and vibration creates the sound. This is because the vibration is one that creates a sensation of sound. The Vibration is nothing but “To and Fro Movement”.
Propagation of Sound Waves
The sound needs a medium to propagate. Example of Medium is Air, water, Thread, Railway Track etc. The sound cannot travel in Vaccum.
This can be observed in the Lab using Electric Bell inside the vacuum jar. As no sound is heard after air is fully removed from the Jar.
Sound moves from one to another point through a medium. When the source of the sound such as an object vibrates, it also vibrates the particles of the medium. This in turn vibrates the other particles near to it. So that each particle vibrates the particles nearby and a wave is created.
As a result, sound vibration travels to the other end. A point to note is, only the vibration move through the medium, not the particle. The particle changes its position and comes back to its original position. All the particles move in “to and fro motion”.
In the wave there are two parts, they are compression and rarefactions. The wave that propagates with compression and rarefactions are known to be Longitudinal waves.
The Longitudinal waves the particles of the medium move “to and fro” in the direction of propagation of the wave.
The sounds are longitudinal.
Compression is an area where the particles of the medium crowded together. Rarefaction is an area where the particles are spread or particle density is low.
Figure 1: Sound is the Longitudinal