Q. The velocity of sound in glass in which two waves of length $50\, cm$ and $50.4\, cm$ produces 6 beats per second is

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A

340 m/s

B

380 m/s

C

378 m/s

D

348 m/s

Solution:

$v=f \lambda\,\, f_{1}=v / \lambda_{1}=v / 50,$
$f_{2}=v / 50.4, f_{b}=f_{1}-f_{2},\,\,6=(v / 50)-(v / 50.4)$
Therefore, $v=378$

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