JEE PHYSICS MCQ: WAVES

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A train moves towards a stationary observer with speed

34\,\,\mathrm{m}{\mathrm{s}^{ - 1}}

. The train sounds a whistle and its frequency registered by the observer is

{f_1}

. If the train’s speed is reduced to

17\,\mathrm{m}{\mathrm{s}^{ - 1}}

, the frequency registered is

{f_2}

. If the peed of sound is

340\,\,\mathrm{m}{\mathrm{s}^{ - 1}}

, then the ratio

{f_1}/{f_2}

View answer and explanation

Correct option: D

\frac{{19}}{{18}}

The correct answer is D (19/18). The ratio of frequencies is calculated using the Doppler effect formula for a moving source approaching a stationary observer, considering the two different speeds of the train.

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