Q. The phase difference between two points separated by $0.8\ m$ in a wave of frequency is $120\ Hz$ is $\pi/2.$ The velocity of wave is
A) $720\ m/s$
B) $384\ m/s$
C) $250\ m/s$
D) $1\ m/s$
Explanation
(b) Phase difference $= \frac{2\pi}{\lambda} \times$ path difference
$\Rightarrow \frac{\pi}{2} = \frac{2\pi}{\pi} \times 0.8 \Rightarrow \lambda = 4 \times 0.8 = 3.2m$
Velocity $v = n\lambda = 120 \times 3.2 = 384\ m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.