JEE PHYSICS MCQ: WAVES

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Application +4 | -1

An observer is standing

500\,\,m

away from a vertically hill. Starting between the observer and the hill a police van having a siren of frequency

1000\,\,Hz

moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is

970\,\,Hz

, the frequency of the sound heard after reflection from the hill (in Hz) is about, (velocity of sound =

330\,\,m{s^{ - 1}}

View answer and explanation

Correct option: B

1032

Option B (

1032

) is correct because it accounts for the Doppler effect twice: once as the van approaches the hill and again as the reflection approaches the observer.

More Questions from WAVES

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The source of sound generating a frequency of

3\,\,kHz

reaches an observer with a speed of

0.5

times, the velocity of sound in air. The frequency heard by the observer is A source of sound emits waves with frequency

f\mathrm{ }Hz

and speed

V\mathrm{ }m/sec

. Two observers move away from this source in opposite directions each with a speed

0.2\,\,V

relative to the source. The ratio of frequencies heard by the two observers will be Assertion: The wave function of a pulse is given by

y = \frac{3}{{{{\left( {2x + 3t} \right)}^2} + 4}},

it propagates in

(– \mathrm{ve}) \,x

-direction.
Reason: The given wave function is of the form

y = f(kx +\omega t),

which represent a wave travelling in negative

X

-direction. In the fundamental mode, time taken by the wave to reach the closed end of the air filled pipe is

0.01\,\,s

. the fundamental frequency is A rope

5 \mathrm{~m}

long has a total mass of

245 \mathrm{~g}

. It is stretched with a constant tension of

1 \mathrm{~kg}

wt. If it is fixed at one end and shaken by hand at the other end, what frequency of shaking will make it break up into three vibrating segments? Take

g=980 \mathrm{~cm} \mathrm{~s}^{-2}

. If

T

is the reverberation time of an auditorium of volume

V

then