A glass tube is open at both the ends.A tuning fork of frequency f resonates with the air column inside the tube. Now the tube is placed vertically inside water so that half the length of the tube is filled with water. Now the air column inside the tube is in unison with another fork of frequency f'. Then

• f' = f

• f' = 4f

• f' = 2f

• f' = f/2

It is possible to recognize a person by hearing his voice even if he is hidden behind a solid wall. This is due to the fact that his voice

• has a definite capacity

• has a definite quality

• has definite pitch

• can penetrate the wall

A source of sound emits 200 $\mathrm{\pi }$W power which is uniformly distributed over a sphere of 10 m radius. What is the loudness of sound on the surface of a sphere?

• 200 dB

• 200π dB

• 120 dB

• 120π dB

A siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s. Frequency of sound to be heard by the listener is (velocity of sound = 330 m/s).

• 286.5 Hz

• 481.2 Hz

• 733.3 Hz

• 644.8 Hz

The musical interval between two tones of frequency 400 Hz and 200 Hz is

• 2

• 200

• 1

• 0.5

A transverse wave is expressed as y = y₀ sin2πfy. For what value of λ, maximum particle velocity is equal to 4 times the wave velocity?

• ${\mathrm{y}}_0\frac{\mathrm{\pi }}{2}$

• $2y_0\mathrm{\pi }$

• $y_0\mathrm{\pi }$

• $\frac{{\mathrm{y}}_0\mathrm{\pi }}{4}$

227.

50 tuning forks are arranged in increasing order of their frequencies such that each gives 4 beats/s with its previous tuning fork. If the frequency of the last fork is octave of the first, then the frequency of the first tuning fork is:

• 200 Hz

• 204 Hz

• 196 Hz

• none of these

The apparent frequency in Doppler's effect does not depend upon:

• speed of the observer

• distance between observer and source

• speed of the source

• frequency from the source

Two simple pendulums whose lengths are 100 cm and 121 cm are suspended side by side. Their bobs are pulled together and then released. After how many minimum oscillations of the longer pendulum, will the two be in phase

• 11

• 10

• 21

• 20

A light source approaches the observer with a velocity of 0.5 c. Doppler's shift for a light of wavelength 5500 Å is:

• 616 Å

• 1833 Å

• 5500 Å

• 6160 Å