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  • Solve it, The driver of a car travelling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is:

The driver of a car travelling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is:

  • Option 1)

    555.5 Hz

  • Option 2)

    720 Hz

  • Option 3)

    500 Hz

  • Option 4)

    550 Hz

 

Answers (2)

best_answer

As discussed

Frequency of sound when observer is stationary and source is moving towards observer -

\nu {}'= \nu _{0}.\frac{C}{C-V_{s}}
 

- wherein

C= speed of sound

V_{s}= speed of source

\nu _{0}= original frequency

\nu {}'= apparent frequency

 

 and

Frequency when observer is stationary and source is moving away from observer -

\nu {}'= \nu _{0}.\frac{C}{C+V_{s}}
 

- wherein

C= speed of sound

V_{s}= speed of source

\nu _{0}= original frequency

\nu {}'= apparent frequency

 

 {v}'=\frac{v}{v-30}v

{v}''=\frac{v}{v-30}{v}'=\frac{v+30}{v-30}v=\frac{360}{300}\times600=720 Hz

 


Option 1)

555.5 Hz

Incorrect

Option 2)

720 Hz

Correct

Option 3)

500 Hz

Incorrect

Option 4)

550 Hz

Incorrect

Posted by

divya.saini

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My answer is 720 Hz.  Thanku yu

 

Posted by

Anjali Nadda

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