Q140 / 160 · TS EAMCET 2024 (09 May Shift 2) · Physics

If three sources of sound of frequencies $(n-1), n$ and $(n+1)$ are vibrated together, the number of beats produced and heard per second respectively are

  • A
    4 and 2
  • B
    4 and 4
  • Correct answer
    C
    2 and 2
  • D
    2 and 4

Solution

$\begin{aligned} & f_1=n-1 \\ & f_2=n \\ & f_3=n+1 \end{aligned}$ $\begin{aligned} \operatorname{maximum} N_0 \text { of beats } & =f_3-f_1 \\ & =n+1-(n-1) \\ \therefore N & =2 \end{aligned}$ $N=2 \text { beats } / \mathrm{sec}$ $\therefore$ No. of beats produced will be 2 beats/sec. $\begin{aligned} \text { No. of heard also } & =n_{\max }-n_{\min } \\ & =(n+1)-(n-1) \\ & =2 \text { beats } / \mathrm{sec} \end{aligned}$ $\therefore$ ANS: (3) 2 and 2

Hence, the correct answer is option: 'C'.

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