Two sources of sound placed close to each other, are emitting progressive waves given by
`y_(1) = 4 sin 600 pi t and y_(2) = 5 sin 608 pi t `
An observer located near these two sources of sound will hear :

Options

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

Answer

A

Explanation

`2 pi v_(1) = 600 pi rArr v_(1) = 300 `Hz
` 2 pi v_(2) = 608 pi rArr v_(2) = 304 `Hz
`therefore b = v_(2) - v_(1) = 4 ` Hz
`(I_(max))/(I_(min)) = ((A_(1) + A_(2))^(2))/(A_(1) - A_(2))^(2) = ((4 + 5)/(4 - 5)) ^(2) = (81)/(1) `.
so correct choice is a.