 # Speed of Sound

## •    Speed of sound is defined as the distance travelled by sound wave per unit time. Mathematically, speed of sound is equal to the product of frequency and wavelength.The speed of sound depends on, the elasticity and the density of the medium. •    The relation of the speed of sound (v) with any given medium is equal to square root of ratio of modulus of elasticity (E) to the density  of the medium. •    Speed of sound is fastest in solids as particles are extremely close to each other taking less time to travel from one end of any solid object to another. In case of liquids and gases particles are far apart as compare to solids and hence, take a little longer time to travel from one end of any to another.•    According to Newton’s assumption when sound travels through gas then it undergoes isothermal process, and the velocity of sound air came out to be 280 metres per second but experimentally the value of velocity of sound in air is nearly equal to 331 metres per second. Later Laplace applied a correction to the newton’s formula stating propagation of sound through gas is an adiabatic change. •    The different factors that affect the speed of sound in gases are effect of density and effect of direction of wind. •    The factors which do not affect the speed of sound in gas are effect of pressure, amplitude and frequency of sound waves. •    Speed of light is much faster than the speed of sound and this fact can be used to find out the speed of sound in air.

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• Q1

Does a 330 Hz sound wave travel faster, slower or at the same speed as 440 Hz sound wave?

Marks:1

It will travel at the same speed as speed of sound does not depend on the frequency.

• Q2

Sound can travel through solids , liquids and gases. Arrange the speed of sound in gases, solids, liquids in an ascending order.

Marks:1

Sound needs material medium to travel and the speed of sound through different mediums arrange in ascending order as: Gases< liquids < Solids

• Q3

Why we see lightning before we hear the thunder?

Marks:1

We see lightning before we hear the sound of thunder because speed of light 3 ×108 m/s is more than the speed of sound (331 m/s).

• Q4

Does the speed of sound depend on pressure?

Marks:1

No, the speed of sound is independent of pressure.