Speed of Sound in Different Medium Class 9 Physics

Speed of Sound in different medium

Dear students, we have already derived the formula for velocity of sound which is given as,

v = f × λ

Where, f is the frequency and λ is wavelength of the wave.

As we know that the speed of sound depends upon the material medium which exists between source of sound and listener. During propagation of sound pressure difference is created due to formation of compression and rarefactions. Crowded particles of medium has more density and pressure whereas the widely spaced particles possesses less density and pressure, this indicates that the speed of sound wave directly relates with the density of material medium through which it is travelling. So let’s discuss the speed of sound in different material medium.

During travelling through different mediums, the speed and wavelength of sound changes but its frequency always remains same as frequency is independent of density of medium.

Speed of sound in solid

We know that solid possesses the maximum density amongst the entire material medium. Due to maximum density of molecules of solid, they carry energy through them more suitably than other medium. Hence sound travels fastest in solid.

Speed of sound in solid

We know that solid possesses the maximum density amongst the entire material medium. Due to maximum density of molecules of solid, they carry energy through them more suitably than other medium. Hence sound travels fastest in solid.

Eg: Speed of sound in Iron is about 6000 m/s.

Speed of sound in liquid

Density of liquids is less than that of solids, so the number of molecules available for transfer of energy in liquid is less as compared to solid, so automatically sound takes little more time to travel through liquid.

Eg: Speed of sound in ocean water is about 1500 m/s.

Speed of sound in liquid

Gas has least density amongst the entire medium, so the number of molecules available for transfer of energy is very less. This makes sound to travel slower as compared to solid and liquid. Hence one can say that the speed of sound is minimum in gases.

Eg: Speed of sound in air is about 340 m/s.

From above discussion we can have final conclusion that,

Speed of sound in solid > Speed of sound in liquid > Speed of sound in gas

Let’s solve the numeric given below to understand the variation of speed of sound in more details.

Ex: 1) The speed of sound in oxygen is 316 m/s. Find the wavelength if frequency of sound is 15000 Hz? If the wavelength of sound in sulphur is 1/3rd of oxygen, find the speed of sound in sulphur.

Ans: voxygen = 316 m/s

f = 15000 Hz

λoxygen = ?

We have, v = fλ

∴voxygen = f × λoxygen

∴ vsulphur = 105 m/s

Ex: 2) Ratio of speeds of sound in air to helium gas is 1:3. If the frequency of sound is 12000 Hz. Find the ratio of wavelength of speed in air to helium.


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