Question

The phase difference between two points separated by $0.8\text{m}$ in a wave of frequency $120\text{Hz}$ is $0.5\pi$. The wave velocity is

• A. $144\text{m/s}$
• B. $256\text{m/s}$
• C. $384\text{m/s}$
• D. $724\text{m/s}$

Answer 1

The correct option is C $384\text{m/s}$

Given
path difference $\Delta x=0.8\text{m}$
Frequency $n=120\text{Hz}$
Phase difference $\Delta \varphi =0.5\pi$

We know that, $\Delta \varphi =\frac{2\pi }{\lambda }\Delta x$
now, $\lambda =\frac{2\pi }{0.5\pi }0.8=3.2\text{m}$

Wave veocity, $v=n\lambda =120\times 3.2=384\text{m/s}$