Question 244: Waves

Question

A sound source is moving towards a stationary observer with $\left(\frac{1}{10}ight)^{	ext {th }}$ the speed of sound, The ratio of apparent to real frequency is

Accepted Answer

Step 1. Formula for Doppler effect when source approaches stationary observer:
$ f' = f \cdot \frac{v}{v - v_s} $
where
$f'$ = apparent frequency
$f$ = source frequency (real)
$v$ = speed of sound
$v_s$ = speed of source (toward observer)
Step 2. Given condition:
$ v_s = 	frac{1}{10} v $
So,
$ \frac{f'}{f} = \frac{v}{v - 	frac{1}{10}v} = \frac{v}{\frac{9}{10} v} $
Step 3. Simplify
$ \frac{f'}{f} = \frac{1}{	frac{9}{10}} = \frac{10}{9} $
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Final Answer:
$ \frac{f'}{f} = \frac{10}{9} $
Correct Option: A.

Answer

$\frac{10}{9}$

Answer

$\frac{11}{10}$

Answer

$\left(\frac{11}{10}\right)^2$

Answer

$\left(\frac{9}{10}\right)^2$

Waves

A sound source is moving towards a stationary observer with \left(\frac{1}{10}\right)^{\text {th }} the speed of sound, The ratio of apparent to real frequency is

Choose the correct answer: