wave_mechanics critical_thinking Question 29
Question: Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously. On changing the tension in one of them, the beat frequency remains unchanged. Denoting by $ T _{1},T _{2} $ , the higher and the lower initial tensions in the strings, then it could be said that while making the above change in tension
[IIT 1991]
Options:
A) $ T _{2} $ was decreased
B) $ T _{2} $ was increased
C) $ T _{1} $ was increased
D) $ T _{1} $ was kept constant
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Answer:
Correct Answer: B
Solution:
Using $ n=\frac{1}{2l}\sqrt{\frac{T}{m}} $ ; As $ T _{1}>T _{2} $
Therefore $ n _{1}>n _{2} $ giving $ n _{1}-n _{2}=6 $ The beat frequency of 6 will remain fixed when (i) $ n _{1} $ remains same but $ n _{2} $ is increased to a new value $ (n _{2}^{\prime }-n _{2}=12) $ by increasing tension $ T _{2} $ .
(ii) n2 remains same but n1 is decreased to a new value $ (n _{1}-n _{1}’=12) $ by decreasing tension T1.
BETA
