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Standard XII

Physics

Beat Frequency

A train moves...

Question

A train moves towards a stationary observer with speed $34 m / s$ . The train sounds a whistle and its frequency registered by the observer is $f_{1}$ . If the speed of the train is reduced to $17 m / s$ , the frequency registered is $f_{2}$ . If speed of sound is $340 m / s$ , then the ratio $f_{1} / f_{2}$ is__?

18 / 17

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19 / 18

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20 / 19

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Solution

The correct option is A $19 / 18$
$f_{a p p} = f_{0} [\frac{v_{2} \pm v_{0}}{v_{2} \mp v_{s}}]$
$f_{1} = f_{0} [\frac{340}{340 - 34}]$
$f_{2} = f_{0} [\frac{340}{340 - 17}]$
$\frac{f_{1}}{f_{2}} = \frac{340 - 17}{340 - 34} = \frac{323}{306} \Rightarrow \frac{f_{1}}{f_{2}} = \frac{19}{18}$ .

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Similar questions

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is $f_{1}$ . If the train's speed is reduced to 17 m/s, the frequency registered is $f_{2}$ . If the speed of sound is 340 m/s then the ratio $\frac{f_{1}}{f_{2}}$ is :

Q. A train moves towards a stationary observer with speed

34 m / s

. The train sounds a whistle and its frequency registered is

f_{1}

. If the train’s speed is reduced to

17 m / s

, the frequency registered is

f_{2}

. If the speed of sound is

340 m / s

then the ratio

\frac{f_{1}}{f_{2}}

Q. A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the train's speed is reduced to 17 m/s, and it moves away from observer the frequency registered is f2. If the speed of sound is 340 m/s then the ratio f1/f2 is -

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered is f1. If the train’s speed is reduced to 17 m/s, the frequency registered is $f_{2}$ . If the speed of sound is 340 m/s then the ratio $\frac{f_{1}}{f_{2}}$ is

Q. A train moves towards a stationary observer with speed

34 m / s

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

f_{1}

. If the trains speed is reduced to

17 m / s

, the frequency registered is

f_{2}

. If the speed is reduced to

340 m / s

then ratio

f_{1} / f_{2}

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A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the speed of the train is reduced to 17 m/s, the frequency registered is f2. If speed of sound is 340 m/s, then the ratio f1/f2 is__?

The correct option is A 19/18fapp=f0[v2±v0v2∓vs]f1=f0[340340−34]f2=f0[340340−17]f1f2=340−17340−34=323306⇒f1f2=1918.

The correct option is A $19 / 18$
$f_{a p p} = f_{0} [\frac{v_{2} \pm v_{0}}{v_{2} \mp v_{s}}]$
$f_{1} = f_{0} [\frac{340}{340 - 34}]$
$f_{2} = f_{0} [\frac{340}{340 - 17}]$
$\frac{f_{1}}{f_{2}} = \frac{340 - 17}{340 - 34} = \frac{323}{306} \Rightarrow \frac{f_{1}}{f_{2}} = \frac{19}{18}$ .