JEE PHYSICS MCQ: WAVES

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Application +4 | -1

A stationary source emits a whistle at a frequency of

200 \mathrm{~Hz}

. If the velocity of propagation of sound is

340 \mathrm{~ms}^{-1}

, then the observed frequency, if the observer is moving away from the source at

25 \mathrm{~ms}^{-1}

, will be

View answer and explanation

Correct option: B

215 \mathrm{~Hz}

Option A (

185 \mathrm{~Hz}

) is incorrect. The correct answer is derived from the Doppler effect formula when the observer is moving away from the source. The correct formula to use is

f' = f \left( \frac{{v}}{{v + v_s}} \right)

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