An observer moves towards a stationary source of sound, with a velocity one­fifth of the velocity of sound. What is the percentage increase in the apparent frequency ?

  • Option 1)

    5%

  • Option 2)

    20%

  • Option 3)

    0

  • Option 4)

    0.5%

 

Answers (1)

As we learnt in

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.

-

 

 

 

By Doppler's effect

\frac\upsilon '\upsilon = \frac\nu _s+\nu\nu (where v_s is the velocity of sound)

\; \; \; \; \; \; \; = \frac\nu+\left ( \nu /5 \right ) \nu = \frac

\therefore \; \; \; \; \; \; \; \; Fractional \: \: increase

                                    \; \; \; \; \; \; \; \; \; \; \; \; \; \; \; \frac\upsilon '-\upsilon \upsilon = \left ( \frac65 -1\right )= \frac15

\therefore \; \; \; \; \; \; \; \; Percentage\: \: increase\: \: = \frac1005=   

Correct option is 2.


Option 1)

5%

This is an incorrect option.

Option 2)

20%

This is the correct option.

Option 3)

0

This is an incorrect option.

Option 4)

0.5%

This is an incorrect option.

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