Q: Two tuning forks of frequency 250 Hz and 256 Hz produce beats. If a maximum is observed just now, after how much time the minimum is observed at the same place ?

(a) 1/18 s

(b) 1/6 s

(c) 1/12 s

(d) 1/24 s

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Ans: (c)

Sol : Beat Frequency , $\displaystyle f_b = |f_2 – f_1| $

$\displaystyle f_b = |256 – 250| $

$\displaystyle f_b = 6 Hz $

Time Period , $\displaystyle T_b = \frac{1}{f_b} = \frac{1}{6} sec $

Time from one maxima to minima , $\displaystyle T = \frac{T_b}{2} $

$\displaystyle T = \frac{1}{12} sec$