Two sources of sound placed close to each other are emitting progressive waves given by `y_1=4sin600pit` and `y_2=5sin608pit`. An observer located near these two sources of sound will hear:

Options

A. 4 beats per second with intensity ratio 25 :16 between waxing and waning
B. 8 beats per second with intensity ratio 25 : 16 between waxing and waning
C. 8 beats per second with intensity ratio 81 : 1 between waxing and waning
D. 4 beats per second with intensity ratio 81 : 1 between waxing and waning

Answer

D

Explanation

`f_(1)=(600pi)/(2pi)=300Hz,A_(1)=4`
`f_(2)=(608pi)/(2pi)=304Hz, A_(2)=5`
`f_("beat")=4Hz`
`(I_(max))/(I_(min))=((A_(1)+A_(2))/(A_(1)-A_(2)))^(2)=(81)/(1)`.