question_answer

A source and listener are both moving towards each other with speed 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 [MP PMT 1994; MP PET 2001]

A)            1.11 f                                       

B)            1.22 f

C)            f     

D)            1.27 f

Correct Answer: B

Solution :

           When source and listener both are moving towards each other then, the frequency heard \[{n}'=n\,\left( \frac{v+{{v}_{O}}}{v-{{v}_{S}}} \right)\] Þ \[{n}'=f\,\left( \frac{v+v/10}{v-v/10} \right)=1.22\,f.\]