Question

An observer is moving with velocity v0 towards a stationary sound source emitting waves of frequency n. If v is the velocity of sound waves, then the wavelength of the sound waves as detected by the observer will be:

Solution

Correct option is

 

Since the observer is moving towards the source, the velocity of sound wave relative to the observer becomes v + v0. As a result, the number of waves, each of wavelength λ, crossing the observer per second, i.e., apparent frequency n’ becomes  

                             

The wavelength observed by the observer will be: 

                   

                     

SIMILAR QUESTIONS

Q1

The speed of sound in oxygen is 635 m/s. Find out the speed of sound in a mixture of hydrogen and oxygen in which the ratio of hydrogen and oxygen volumes is 4:1.

Q2

Find out the ratio of the velocity of sound in helium and in nitrogen gases at 300 K temperature. Molecular weights of helium and nitrogen are 4 and 28 respectively.

Q3

At what temperature will the speed of sound in air be double of its speed at 57oC?

Q4

At what temperature the speed of sound in oxygen will be same as that in nitrogen at 14oC? The molecular weights of oxygen and nitrogen are 32 and 28 respectively.

Q5

A wave whose amplitude is 0.07 m and frequency is 400 hertz travels in a medium with a velocity of 300 m/s. Determine the displacement equation of oscillation at a distance x metre from the source due to this wave.

Q6

The intensity of a sound wave gets reduced by 20% on passing through a slab. The reduction in intensity on passage through two such consecutive slabs is:

Q7

A is singing a note and at the same time B is singing a note with exactly one-eighth the frequency of the note of A. The energies of the two sounds are equal. The amplitude of the note of B is:

Q8

A twofold increase in the intensity of a wave implies an increase of:

Q9

An increase in intensity level of one decibel implies an increase in intensity of:

Q10

A rocket ship is receding from the earth at a speed of 0.2 c. The ship emits the signal of frequency  The apparent frequency to an observer on the surface of the earth is: