Characteristics of a sound wave

Class 9th NCERT SCIENCE Course Sound Free Lessons for Class 9th Physics Characteristics of a sound wave

Sound wave is longitudinal wave consisting of compression and rarefaction traveling through a medium
To describe a sound wave we need to know five terms
Time Period,Frequency,Wavelength,Amplitude,and Velocity

In the Above Image

Sound Wave ABCDE and EFGHI .
It starts from position A (normal density position) and compress along ABC and Rarefaction along CDE
Again it returns to its normal position E
Thus The ABCDE portion shows a complete Wave

Wavelength-

The Minimum Distance in which a sound wave repeats itself is called its wavelength
It is denoted by the symbol lambda λ
The Combined length of one compression and rare fraction is called its wavelength
In the above figure the combined length of AC and CE means the length ACE is the wavelength
The SI unit of wavelength is Meter

Amplitude

When a wave passes through a medium ,the particles of the medium gets displaced temporarily from their original position
In the Figure PB is the Amplitude
The maximum displacement of the particle of the medium from their original undisturbed position is called amplitude
The SI unit of Amplitude is Meter

Time Period

The Time required to produce one complete wave is called time period
You can say the time taken to travel from Point A to point E is the time period
The Unit of time period is Second

Frequency

The Number of complete cycles produced in one second is called Frequency
The Unit of frequency is Hertz Hz.

Also F= 1/t

Where Frequency = 1/ Time Period

Velocity Of Wave(Speed of wave)

The distance traveled by a wave in one second is called its velocity.
Its unit is M/S

The Relationship between frequency wavelength and velocity

Example

If 25 sound waves are produced per second,what is the frequency in hertz.

Ans. As the name Says Frequency is equal to number of waves produced in a second .hence frequncy is equal to 25 hertz.

Now Another Problem

2.The Wavelength of a sound emitted by a source is 1.7 × 10 ^-2 m. calculate the Frequency of the sound if its velocity is 343.4 m/s .

Solution

The Relationship between frequency wavelength and velocity is given by

v= f ×λ

v= velocity of the wave

f=frequency

λ= Wavelength

Velocity of the wave = Frequency × Wavelength

So 343.4 = f × 1.7 × 10 ^-2 m

f = 2.02 × 10⁴ Hz.

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