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A musician using an open flute of length 50cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10km/h. If the wave speed is 330m/s, the frequency heard by the running person shall be close to:

 

  • Option 1)

    666Hz

  • Option 2)

    500 Hz

  • Option 3)

    333 Hz

  • Option 4)

    753 Hz

Answers (1)

best_answer

 

Doppler Effect -

When a source of sound and a listener are in motion relative to each other, the frequency of the sound heard by the listener is not the same as the source frequency.

-

Frequency produced by flute 

f=2(\frac{V}{2l})=\frac{2\times 330}{2\times 0.5}=660\: Hz

Velocity of obserever = 10\times \frac{5}{18}=\frac{25}{9}\: m/s

Frequency of observer

f_{o}=\left [ \frac{V+V_{o}}{V} \right ]f

     =\left [ \frac{\frac{25}{9}+330}{330} \right ]660

    =671.12

 


Option 1)

666Hz

Option 2)

500 Hz

Option 3)

333 Hz

Option 4)

753 Hz

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