Characteristics of a sound wave — lesson. Science State Board, Class 9.

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A sound wave can be explained completely by five characteristics; they are

Amplitude
Frequency
Time period
Wavelength
Velocity or speed

Wave nature

Amplitude ( $A$ ):

The wave's amplitude is the maximum displacement of medium particles from their original undisturbed positions when a wave passes through the medium. The sound will be loud if the vibration of a particle has a large amplitude and soft if the vibration has a small amplitude. 'A' stands for amplitude. The

$metre$

$m$ is its SI unit.

Time period ( $T$ ):

The time taken for one complete oscillation of a sound wave is called the time period of the sound wave.

$Time period = \frac{1}{Frequency}$
Frequency ( $F$ ):

The number of oscillations an object takes per second is called its frequency.
The SI unit of frequency is

$Hertz$ (

$Hz$ ).

$Frequency = \frac{Total number of oscillations}{Total time taken}$

Velocity or Speed of the sound ( $v$ ):

The speed of sound is defined as the distance that sound travels in one second. The letter ‘

$v$ ' stands for it.

It is mathematically represented as,

$v = n λ$

where '

$n$ ' is the frequency and '

$λ$ ' is the wavelength.

Distance travelled by the sound wave is found by,

$Distance (d) = Number of waves \times Wavelength (λ)$

Example:

A sound has a frequency of

$70$

$Hz$ and a wavelength of

$10$

$m$ . What is the speed of the sound?

Solution:

Frequency (

$n$ )

$=$

$70$

$Hz$

Wavelength (

$λ$ )

$=$

$10$

$m$

To find: Speed of the sound (

$v$ )

We know the formula,

$v = n λ$

By applying these values we get,

$v$

$=$

$70 \cdot 10$

$v$

$=$ 700

$m / s$

$1$

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4. Characteristics of a sound wave

Theory: