The difference between the apparent frequency of a source of sound as perceived by the observer during its approach and recession is 2% of the frequency of the source. If the speed of sound in air is 300 ms^-1, the velocity of the source is

• 1.5 ms^-1

• 12 ms^-1

• 6 ms^-1

• 3 ms^-1

The loudness and pitch of a sound note depend on

• intensity and velocity

• frequency and velocity

• intensity and frequency

• frequency and number of harmonics

73.

In Melde's experiment in the transverse mode, the frequency of the tuning fork and the frequency of the waves in the string are in the ratio

• 2 : 1

• 4 : 1

• 1 : 1

• 1 : 2

If two waves of the same frequency and amplitude respectively on superposition produce a resultant disturbance ofthe same amplitude, the waves differ in phase by

• $\mathrm{\pi }$

• zero

• $\mathrm{\pi }/3$

• $2\mathrm{\pi }/3$

A man, standing between two cliffs, claps his hands and starts hearing a series of echoes at intervals of one second. If the speed of sound in air is 340 ms^-1, the distance between the cliffs is

• 680 m

• 1700 m

• 340 m

• 1620 m

Sound waves in air are always longitudinal because

• of the inherent characteristics of sound waves in air

• air does not have a modulus of rigidity

• air is a mixture of several gases

• density of air is very small

A particle on the trough of a wave at any instant will come to the mean position after a time (T = time period)

• T/2

• T/4

• T

• 2T

The disc of a siren containing 60 holes rotates at a constant speed of 360 rpm. The emitted sound is in unison with a tuning fork of frequency

• 10 Hz

• 360 Hz

• 216 Hz

• 60 Hz

The ratio of velocity of sound in hydrogen and oxygen at STP is

• 16 : 1

• 8 : 1

• 4 : 1

• 2 : 1

In an experiment with sonometer a tuning fork of frequency 256 Hz resonates with a length of 25 cm and another tuning fork resonates with a length of 16 cm. Tension of the string remaining constant the frequency of the second tuning fork is

• 163.84 Hz

• 400 Hz

• 320 Hz

• 204.8 Hz