Waves Ques 63
63. A source of sound gives $5$ beats per second, when sounded with another source of frequency $100 / sec$. The second harmonic of the source, together with a source of frequency $205 / sec$ gives $5$ beats per second. What is the frequency of the source?
[1995]
(a) $95 $ $sec^{-1}$
(b) $100 $ $sec^{-1}$
(c) $105 $ $sec^{-1}$
(d) $205 $ $sec^{-1}$
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Answer:
Correct Answer: 63.(c)
Solution:
- (c) Frequency of first source with $5$ $beats/ sec $ $=100 $ $Hz$ and frequency of second source with $5$ $beats / sec=205 $ $Hz$. The frequency of the first source $=100 \pm 5=105$ or $95 $ $Hz$.
Therefore, frequency of second harmonic of source $=210$ $Hz$ or $190 $ $Hz$.
As the second harmonic gives $ 5$ $ beats/ second$ with the sound of frequency $205 $ $Hz$, therefore, frequency of second harmonic source should be $210 $ $Hz$ or frequency of source $=105 $ $Hz$.
BETA
