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 .

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An observer $A$ is moving directly towards a stationary sound source while another observer $B$ is moving away from the source with the same velocity. Which of the following statements are correct?

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Important Questions on Sound Waves and Doppler Effect

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

Consider a source of sound

S

and an observer

P .

The sound source is of frequency

n_{0} .

The frequency observed by

P

is found to be

n

, if

P

approaches

S

at speed

v

and

S

is stationary;

n_{2}

S

approaches

P

at a speed

v

and

P

is stationary and

n_{3}

if each of

P

and

S

has speed

v / 2

towards one another. Now,

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 4

Which of the following statements are incorrect?

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 5

A source

S

of sound wave of fixed frequency

N

and an observer

O

are located in air initially at the space points

A

and

B

, a fixed distance apart. State in which of the following cases, the observer will

NOT

see any Doppler effect and will receive the same frequency

N

as produced by the source.

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 8 - Sound Waves and Doppler Effect>Exercises>Q 6

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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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).

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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

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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?

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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}

An observer A is moving directly towards a stationary sound source while another observer B is moving away from the source with the same velocity. Which of the following statements are correct?

Important Questions on Sound Waves and Doppler Effect

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An observer $A$ is moving directly towards a stationary sound source while another observer $B$ is moving away from the source with the same velocity. Which of the following statements are correct?