A string 2.0, m long and fixed at its end is driven by a 240, Hz vibrator. string vibrates in its th

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14.Waves and Sound

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A string $2.0\, m$ long and fixed at its end is driven by a $240\, Hz$ vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is

A

$320\, m/s, 120\, Hz$

B

$180\, m/s, 80\, Hz$

C

$180\, m/s, 120\, Hz$

D

$320\, m/s, 80\, Hz$

(JEE MAIN-2019)

Solution

We have:

$f=\frac{n v}{2 \ell}$

$240=\frac{3 \times v}{2 \times 2}$

$\Rightarrow \quad v=320 \mathrm{m} / \mathrm{s}$

Fundamental frequency $=\frac{v}{2 \ell}=80 \mathrm{Hz}$

Standard 11

Physics

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