Question

When a source of frequency f₀ moves away a stationary observer with a certain velocity an apparent frequency f ' is observed. When it moves with same velocity towards the observer, the observed frequency is 1.2 f '. If velocity of sound in v, then the speed of source is –

• A. $\frac{v}{6}$
• B. $\frac{v}{11}$
• C. $\frac{3}{4}v$
• D. None of these

Answer 1

Answer: (B)

$\frac{v}{11}$

Answer 2

f ' = f₀ $\left( \frac { v } { v + u } \right)$ and 1.2 f ' = f₀ $\left( \frac { v } { v - u } \right)$

\ 1.2 = $\frac { v + u } { v - u }$ ̃ u =