Question

A source of sound is travelling towards a stationary observer. The frequency of sound heard by the observer is of three times the original frequency. The velocity of sound is v m/sec. The speed of source will be

• A. $\frac{2}{3}v$
• B. v
• C. $\frac{3}{2}v$
• D. 3v

Answer 1

Answer: (A)

$\frac{2}{3}v$

Answer 2

$n^{'} = n\left( \frac{v}{v - v_{S}} \right)$⇒$\frac{n'}{n} = \frac{v}{v - v_{S}} \Rightarrow \frac{v}{v - v_{S}} = 3 \Rightarrow v_{s} = \frac{2v}{3}$