Question

The phase difference between two points separated by 1 m in a wave of frequency 120 Hz is 90?. The wave velocity will be:

• A. 720 m/s
• B. 480 m/s
• C. 240 m/s
• D. 180 m/s

Answer 1

Answer: (B)

Here: path difference $\Delta x=1m$ Phase difference $={90}^o=0.5\pi$ Frequency $n=120Hz$ $\therefore$ Phase difference $\text{o }|\text{ =}\frac{2\pi }{\lambda }\times \Delta x$ or $\lambda =\frac{2\pi \times \Delta x}{\text{o }|}=\frac{2\pi \times 1}{0.5\pi }=4m$ Hence, wave velocity $\upsilon =n\lambda =120\times 4=480m/s$