• # question_answer 39) 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: A)  4 beats per second with intensity ratio 81:1 between waxing and waningB)  4 beats per second with intensity ratio 25 : 16 between waxing and waningC)  8 beats per second with intensity ratio 25 : 16 between waxing and waningD)  8 beats per second with intensity ratio 81: 1 between waxing and waning

$\frac{{{I}_{1}}}{{{I}_{2}}}=\frac{({{A}_{1}}+{{A}_{2}})}{({{A}_{1}}-{{A}_{2}})}=\frac{81}{1}$ Beat frequency = 304 - 300 = 4 Hz.