Revision: Sound Physics HSC Science (General) 11th Standard Maharashtra State Board

The distance travelled by a wave in one time period of vibration of the particle of the medium, is called the wavelength (λ).

The distance travelled by the wave in one second is called the wave velocity (V).

If the vibrations of medium particles are along the direction of propagation of the wave, thus forming compressions and rarefactions in the medium, the wave is called a longitudinal wave.

If the medium particles vibrate normal to the direction of propagation of the wave, forming crests and troughs, the wave is called a transverse wave.

The wavelength of a sound wave is the spatial distance over which the wave's shape repeats. Because sound is a longitudinal wave, it is specifically defined as the distance between two consecutive points in the same phase of vibration.

The process by which bats and dolphins detect the presence of an obstacle by hearing the echo of the sound produced by them is called sound ranging. 

The time period of a particle executing S.H.M. is the time taken to complete one cycle and is denoted by T.

The linear distance between the two consecutive particles of a vibrating medium in the same phase is called its wavelength. It is denoted by the Greek letter lambda (λ).

Our ears are sensitive only to a limited range of frequencies from 20 Hz to 20,000 Hz, which is called the audible range of frequency.

The sound of frequency above 20,000 Hz is called ultrasonic.

The sound of frequency below 20 Hz is called infrasonic.

When a sound wave travels in a medium, the maximum displacement of the particle of the medium on either side of its mean position, is called the amplitude (a) of the wave.

The time taken by the particle of the medium to complete its one vibration, is called the time period (T) of the wave.

The number of vibrations made by the particle of the medium in one second, is called the frequency (j) of the wave.

Waves in which a disturbance created at one place travels to distant points and keeps travelling unless stopped by an external force are known as travelling or progressive waves.

Wavelength (λ): The distance between two successive particles which are in the same state of vibration is called the wavelength of the wave. SI unit is (m).

Amplitude (A): The largest displacement of a particle of a medium through which the wave is propagating, from its rest position, is called the amplitude of that wave. SI unit is (m).

The sound heard after reflection from a distant obstacle (such as a cliff, a hillside, wall of a building, edge of a forest, etc.) after the original sound has ceased, is called an echo.

The apparent change in the frequency of sound heard by a listener, due to relative motion between the source of sound and the listener is called Doppler effect in sound.

When the source and the observer are in relative motion with respect to each other and to the medium in which sound propagates, the frequency of the sound wave observed is different from the frequency of the source. This phenomenon is called Doppler Effect.