Question

A source and listener are both moving towards each other with speed $\frac{v}{10}$ where v is the speed of sound. If the frequency of the note emitted by the source is f, the frequency heard by the listener would be nearly

• A. 0.75 f
• B. 1.22 f
• C. f
• D. 2f

Answer 1

The correct option is B 1.22 f

$n^{\prime }=\left(\frac{v+v_L}{v-v_s}\right)n\Rightarrow n^{\prime }=\left(\frac{v+\frac{v}{10}}{v-\frac{v}{10}}\right)n\Rightarrow n^{\prime }=\frac{11}{9}f=1.22f$