A source of unknown frequency gives 4 beats/s when sounded with a source of known frequency 250 Hz. The second harmonic of the source of unknown frequency gives five beats per second when sounded with a source of frequency 513 Hz. The unknown frequency is

(a) 254 Hz (b) 246 Hz (c) 240 Hz (d) 260 Hz

Concept Questions :-

Beats
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Difficulty Level:

When a string is divided into three segments of lengths  the fundamental frequencies of these three segments are  respectively. The original fundamental frequency (v) of the string is

(a) $\sqrt{v}=\sqrt{{v}_{1}}+\sqrt{{v}_{2}}+\sqrt{{v}_{3}}$

(b) $v={v}_{1}+{v}_{2}+{v}_{3}$

(c) $\frac{1}{v}=\frac{1}{{v}_{1}}+\frac{1}{{v}_{2}}+\frac{1}{{v}_{3}}$

(d) $\frac{1}{\sqrt{v}}=\frac{1}{\sqrt{{v}_{1}}}+\frac{1}{\sqrt{{v}_{2}}}+\frac{1}{\sqrt{{v}_{3}}}$

Concept Questions :-

Travelling wave on string
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Difficulty Level:

Two sources of sound placed close to each other, are emitting progressive waves given by

${\mathrm{y}}_{1}$=4 sin 600$\mathrm{\pi t}$ and ${\mathrm{y}}_{2}$=5 sin 608 $\mathrm{\pi t}$

An observer located near these two sources of sound will hear

(a)4 beats per second with intensity ratio 25:16 between waxing and waning

(b) 8 beats per second with intensity ratio 25:16 between waxing and waning

(c) 8 beats per second with intensity ratio 81:1 between waxing and waning

(d) 4 beats per second with intensity ratio 81:1 waxing and waning

Concept Questions :-

Beats
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Difficulty Level:

The equation of a simple harmonic wave is

given by

where x and y are in meters and t is in

seconds. The ratio of maximum particle

velocity to the wave velocity is

(a) $2\mathrm{\pi }$

(b) $\frac{3}{2}\mathrm{\pi }$

(c) $3\mathrm{\pi }$

(d) $\frac{2}{3}\mathrm{\pi }$

Concept Questions :-

Speed of sound
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Difficulty Level:

A train moving at a speed of 220 ${\mathrm{ms}}^{-1}$

towards a stationary object, emits a sound

of frequency 1000 Hz. Some of the sound

reaching the object gets reflected back to

the train as echo. The frequency of the echo

as detected by the driver of the train is

(speed of sound in air is 330 ${\mathrm{ms}}^{-1}$)

(a) 3500Hz

(b) 4000Hz

(c) 5000Hz

(d) 3000Hz

Concept Questions :-

Doppler effect
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Difficulty Level:

Two waves are represented by the equations

and

, where x is in metre

and t in second. The phase difference between

them is

Concept Questions :-

Wave motion
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Difficulty Level:

Sound waves travel at 350 m/s through a warm

air and at 3500 m/s through brass. The wavelength

of a 700 Hz acoustic wave as it enters brass from

warm air :

(a) increases by factor 20

(b) increases by factor 10

(c) decreases by factor 20

(d) decreases by factor 10

Concept Questions :-

Wave motion
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Difficulty Level:

Two identical piano wires kept under the same tension T have a fundamental frequency of 600 Hz. The fractional increase in the tension of one of the wires which will lead to the occurrence of 6 beats/s when both the wires oscillate together would be :

(a) 0.02                                            (b) 0.03

(c) 0.04                                             (d) 0.01

Concept Questions :-

Beats
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Difficulty Level:

Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite directions when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase difference is :

(a)zero                                  (b)$\frac{2\mathrm{\pi }}{3}$

(c)$\mathrm{\pi }$                                      (d)$\frac{\mathrm{\pi }}{6}$

Concept Questions :-

Wave motion
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Difficulty Level:

A transverse wave is represented by y= For what value of the wavelength is the wave velocity equal to the maximum particle velocity?

(a)                                            (b)

(c)                                             (d) A

Concept Questions :-

Types of waves