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A vibrating string of certain length l under a tension T resonates with a mode corresponding to the first overtone (third harmonic) of an air column of length 75 cm inside a tube closed at one end. The string also generates 4 beats/s when excited along with a tuning fork of frequency n. Now when the tension of the string is slightly increased the number of beats reduces to 2 per second. Assuming the velocity of sound in air to be 340 m/s, the frequency n of the tuning fork in Hz is

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Important Questions on Waves

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

Two vibrating strings '

A

' and '

B

' produce beats of frequency

8 Hz

. The beat frequency is found to reduce to

4 Hz

if the tension in the string

' A'

is slightly reduced. If the original frequency of

A

320 Hz

, then the frequency of

B

' is

EASY

Physics>Oscillations and Waves>Waves>Beats

A source of sound gives

5

beats per second when sounded with another source of frequency

100 s^{- 1} .

The second harmonic of the source together with a source of frequency

205 s^{- 1}

gives

5

beats per second. The frequency of the source is

EASY

Physics>Oscillations and Waves>Waves>Beats

Two sound waves with wavelengths

5.0 m

and

5.5 m

, respectively, each propagates in gas with velocity

330 m s^{- 1}

. The number of beats that can be expected from them per second is

EASY

Physics>Oscillations and Waves>Waves>Beats

A set of

20

tuning forks is arranged in a series of increasing frequencies. If each fork gives

4

beats with respect to the preceding fork and the frequency of the last fork is twice the frequency of the first, then the frequency of last fork is _____

Hz

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

The correct figure that shows, schematically, the wave pattern produced by the superposition of two waves of frequencies

9 H z

and

11 H z

, is

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

The velocity of sound in a gas, in which two wavelengths

4.08 m

and

4.16 m

produce

40

beats in

12 s

, will be

EASY

Physics>Oscillations and Waves>Waves>Beats

A tuning fork

A

of unknown frequency produces

5 beats s^{- 1}

with a fork of known frequency

340 Hz

. When fork

A

is filed, the beat frequency decreases to

2 beats s^{- 1}

. What is the frequency of fork

A

HARD

Physics>Oscillations and Waves>Waves>Beats

Two men are walking along a horizontal straight line in the same direction. The man in front walks at a speed

1 .0 m s^{- 1}

and the man behind walks at a speed

2 .0 m s^{- 1}

. A third man is standing at a height

12 m

above the same horizontal line such that all three men are in a vertical plane. The two walking men are blowing identical whistles which emit a sound of frequency

1430 Hz

. The speed of sound in air is

330 m s^{- 1}

. At the instant, when the moving men are

10 m

apart, the stationary man is equidistant from them. The frequency of beats in

Hz

, heard by the stationary man at this instant, is __________.

EASY

Physics>Oscillations and Waves>Waves>Beats

In a guitar, two strings

A

and

B

made of same material are slightly out of tune and produce beats of frequency

6 Hz

. When tension in

B

is slightly decreased, the beat frequency increases to

7 Hz

. If the frequency of

A

530 Hz

, the original frequency of

B

will be:

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

A closed organ pipe and an open organ pipe of same length produce

2 beats \sec^{- 1}

when they are set into vibrations together in fundamental mode. The length of open pipe is now halved and that of closed pipe is doubled. The number of beats produced will be

EASY

Physics>Oscillations and Waves>Waves>Beats

A tuning fork vibrates with frequency

256 Hz

and gives one beat per second with the third normal mode of vibration of an open pipe. What is the length of the pipe? (speed of sound in air is

340 m s^{- 1}

)

EASY

Physics>Oscillations and Waves>Waves>Beats

Three sound waves of equal amplitudes have frequencies,

(n - 1), n, (n + 1)

. They superimpose to give beats. The number of beats produced per second will be

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

An observer is riding on a bicycle and moving towards a hill at

18 km h^{- 1}

. He hears a sound from a source at some distance behind him directly as well as after its reflection from the hill. If the original frequency of the sound as emitted by source is

640 Hz

and velocity of the sound in air is

320 m s^{- 1}

, the beat frequency between the two sounds heard by observer will be _____

Hz

EASY

Physics>Oscillations and Waves>Waves>Beats

Two tuning forks have frequencies

450 Hz

and

454 Hz

respectively. On sounding these forks together, the time interval between two successive maximum intensities will be _______.

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

A source of sound emitting at a frequency

f

is moving towards a wall with speed

v_{b}

. If

v

is the speed of sound then the beat frequency heard by a stationary observer behind the source is

EASY

Physics>Oscillations and Waves>Waves>Beats

An air column, closed at one end and open at the other, resonates with a tuning fork when the smallest length of the column is

50 cm

. The next larger length of the column resonating with the same tuning fork is:

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

A uniform rope of length

L

and mass

m_{1}

, hangs vertically from a rigid support. A block of mass

m_{2}

is attached to the free end of the rope. A transverse pulse of wavelength

λ_{1}

is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is

λ_{2}

. The ratio

\frac{λ_{2}}{λ_{1}}

is:

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

The frequency of two tuning forks

A

and

B

are

1.5 %

more and

2.5 %

less than that of the tuning fork

C

. When

A

and

B

are sounded together,

12

beats are produced in

1

second. The frequency of tuning fork

C

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

A toy-car, blowing its horn, is moving with a steady speed of

5 m s^{- 1}

, away from a wall. An observer, towards whom the toy car is moving, is able to hear

5

beats per second. If the velocity of sound in air is

340 m s^{- 1}

the frequency of the horn of the toy car is close to

MEDIUM

Physics>Oscillations and Waves>Waves>Beats

Two sitar strings,

A

and

B

playing the note '

D h a

' are slightly out of tune and produce beats of frequency

5 Hz

. The tension of the string

B

is slightly increased and the beat frequency is found to decrease by

3 Hz

. If the frequency of

A

425 Hz

. The original frequency of

B

Important Questions on Waves

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