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
4 beats per second with intensity ratio 25 : 16 between waxing and waning
8 beats per second with intensity ratio 25 : 16 between waxing and waning
8 beats per second with intensity ratio 81 : 1 between waxing and waning
4 beats per second with intensity ratio 81 : 1 between waxing and waning
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The Correct Option isD
Solution and Explanation
The correct answer is D:4 beats per second with intensity ratio \(81\ratio 1\) between waxing and waning Comparing with \(y _{1}= a _{1} \sin 2 \pi f _{1} t\) and \(y _{2}= a _{2} \sin 2 \pi f _{2} t\) we get \(f_1 =300\, Hz,\, f _{2}=304\, Hz\) Number of beats \(= f _{2}- f _{1}=4\, s ^{-1}\) \(\frac{ I _{\max }}{ I _{\min }}=\left(\frac{ a _{1}+ a _{2}}{ a _{1}- a _{2}}\right)^{2}\) \(=\frac{ I _{\max }}{ I _{\min }}=\left(\frac{4+5}{4-5}\right)^{2}=\frac{81}{1}\)
Let’s see from fig.m, the frequency of a pink-colored wave is f1, and that of a green-colored wave is f2. So, the frequency of the beat is the difference between these two, which is:
fBEATS = |f1 - f2|
Interference and Beats
When two or more waves travelling in a medium meet, the resulting phenomenon is called interference and beats are an excellent example of the phenomenon of interference.
What is Interference?
When two or more waves travelling in a medium meet, the resulting phenomenon is called interference and beats are an excellent example of the phenomenon of interference.
The Application of Beats:
Beats are used in determining the unknown frequency
Beats are used in determining the existence of poisonous gases in mines.
