Question

A student wants to establish a standing wave on a wire 1.8 m long clamped at both ends. If the wave speed is 72 m/s, what is the minimum frequency she should apply to set up standing waves?

20 Hz

12 Hz

24 Hz

15 Hz

18 Hz

Clear selection

Answer 1

$\lambda= vT=\frac{v}{f};$

$f=\frac{v}{\lambda};$

$\lambda= \frac{2l}{n};$

$f=\frac{v}{2l}*n;$

$\text {as f min } n=1;$

$f=\frac{v}{2l}= \frac{72}{2*1.8} = 20$

$\text{Answer:}20 \ Hz$