Question

A sound wave of frequency $80$ Hz is traveling with speed $320$ m/s .
(a) find the change in phase at a given position in $400$ ms interval .

Answer 1

Here, frequency $\left(n\right)=80Hz$

speed $\left(v\right)=320m/s$

$\lambda =\frac{v}{n}=\frac{320}{80}=4$

In $400ms$, the distance travelled by

particle $={\Delta }^{\ast }=320\times 400\times {10}^{-3}$

so, phase difference $\varphi =2\pi /\lambda {\Delta }^{\ast }$

$=\frac{2\pi }{320}\times 80\times 320\times 400\times {10}^{-3}$

$=64\pi$