In the figure shown an observer O 1 floats (static) on water surface with ears in air while another observer O 2 is moving upwards with constant velocity V 1 = V 5 in water. The source moves down with constant velocity V s = V 5 and emits sound of frequency f ' . The velocity of sound in air is V and that in water is 4 V . For the situation shown in figure.

The wavelength of the sound received by O 2 is 16 V 5 f .

The wavelength of the sound received by O 1 is V f .

Two loudspeakers M and N are located 20 m apart and emit sound at frequencies 118 Hz and 121 Hz , respectively. A car is initially at a point P , 1800 m away from the midpoint Q of the line M N and moves towards Q constantly at 60 km h - 1 along the perpendicular bisector of M N . It crosses Q and eventually reaches a point R , 1800 m away from Q . Let ν t represent the beat frequency measured by a person sitting in the car at time t . Let ν p , ν Q and ν R be the beat frequencies measured at locations P , Q and R , respectively. The speed of sound in air is 330 m s - 1 . Which of the following statement(s) is (are) true regarding the sound heard by the person?

The plot below represents schematically the variations of beat frequency with time

Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. The wind blows along the road with velocity w . One of these vehicles blows a whistle of frequency f 1 . An observer in the other vehicle hears the frequency of the whistle to be f 2 . The speed of sound in still air is v . The correct statement (s) is (are):

If the wind blows from the source to the observer, f 2 > f 1 .

If the wind blows from the observer to the source, f 2 < f 1 .

If the wind blows from the source to the observer, f 2 < f 1 .

MEDIUM

Physics

IMPORTANT

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A vibrating tuning fork is first held in the hand and then its end is brought in contact with a table. Which of the following statement(s) is/are correct in respect of this situation?

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Important Questions on Sound Waves and Doppler Effect

MEDIUM

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 7

A source of sound and detector are moving as shown in the given figure at $t = 0$ . Take velocity of sound wave to be $v .$

Question Image

For this situation mark out the correct statement(s).

MEDIUM

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 8

Plane harmonic waves of frequency

500 Hz

are produced in air with displacement amplitude of

10 μ m

. Given that density of air is

1.29 kg / m^{3}

and speed of sound in air is

340 m / s

. Then

HARD

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 9

A sonic source, located in a uniform medium, emits waves of frequency

n

. If intensity, energy density (energy per unit volume of the medium) and maximum speed of oscillations of medium particle are, respectively

I

E

and

u_{0}

at a point, then which of the following graphs are correct?

HARD

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 10

A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency

1000 H z

normally towards a reflecting wall. The wall approaches the car with a speed of

3.3 m s^{- 1}

HARD

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 11

In the figure shown an observer $O_{1}$ floats (static) on water surface with ears in air while another observer $O_{2}$ is moving upwards with constant velocity $V_{1} = \frac{V}{5}$ in water. The source moves down with constant velocity $V_{s} = \frac{V}{5}$ and emits sound of frequency $f^{'} .$ The velocity of sound in air is $V$ and that in water is $4 V$ . For the situation shown in figure.

Question Image

MEDIUM

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 1

The average power transmitted across a cross-section by two sound waves moving in the same direction are equal. The wavelengths of two sound waves are in the ratio of

1 : 2

, then find the ratio of their pressure amplitudes.

EASY

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 2

The resultant loudness at a point

P

n dB

higher than the loudness of

S_{1}

which is one of the two identical sound sources

S_{1}

and

S_{2}

reaching at that point in phase. Find the value of

n

EASY

Physics

IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 3

The intensity of sound from a point source is

1.0 \times 10^{- 8} W / m^{2}

at a distance of

5.0 m

from the source. What will be the intensity at a distance of

25 m

from the source?

(

\times 10^{- 10} W / m^{2})

A vibrating tuning fork is first held in the hand and then its end is brought in contact with a table. Which of the following statement(s) is/are correct in respect of this situation?

Important Questions on Sound Waves and Doppler Effect

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