here is a question i was solving and confused between 2 ans 2 persons A and B, each carrying a source of sound of frequency f, are standing a few metres apart in a quiet field. A starts moving towards B with a speed u. If v is the speed of sound, the number beats heard per second by A will be so A is the observer,velocity of the observer is u and on applying in the equation we get apparent frequency as (v+u/v) f and beats as fu/v But if i consider A at rest, relative velocity of B will be -u( i.e towards A with a speed u). From this i get appparent frequency as (v/v+u)f and beats as (v/v-u)f. help me to identify which is correct

here is a question i was solving and confused between 2 ans

 

2 persons A and B, each carrying a source of sound of frequency f, are standing a few metres apart in a quiet field. A starts moving towards B with a speed u. If v is the speed of sound, the number beats heard per second by A will be

 

so A is the observer,velocity of the observer is u and on applying in the equation we get apparent frequency as (v+u/v) f and beats as fu/v

 

But if i consider A at rest, relative velocity of B will be -u( i.e towards A with a speed u). From this i get appparent frequency as (v/v+u)f and beats as (v/v-u)f.

 

help me to identify which is correct