Question

Two points on a travelling wave having frequency $500Hz$ and velocity $300m/s$ are $60^{\circ }$ out of phase, then the minimum distance between the two points is

• A. 0.2
• B. 0.1
• C. 0.5
• D. 0.4
• E. None of these

Answer 1

Answer: (B)

As, $v=n\lambda$
$\therefore \lambda =\frac{v}{n}=\frac{300}{500}=\frac{3}{5}m$
Now, phase difference =$\frac{2\pi }{\lambda }\times$ path difference
$\therefore 66^{\circ }=\frac{2\pi }{\lambda }\times$ path difference
or $\frac{60^{\circ }\times \pi }{180^{\circ }}=\frac{2\pi \times 5}{3}\times x$ path difference
Path difference =$\frac{3\times 60\times \pi }{2\pi \times 5\times 180}=0.1$