Question

The figure shows an instantaneous profile of a rope carrying a progressive wave moving from left to right, then?

• A. The phase at A is greater than the phase at B
• B. The phase at B is greater than the phase at A
• C. A is moving upwards
• D. B is moving upwards

Answer 1

The correct option is D B is moving upwards

Vel of $A$ at $t=0$ should be downward and that of $B$ should be upward.

By the given information,

we can assumed

$y=A\sin (kx-ust+\varphi )$

for $A,y=0$ and $x=0,t=0$

$\Rightarrow 0=A(0+0+\varphi )$

For $B,y=0,x=\frac{\pi }{k},t=0$

$\Rightarrow 0=A\sin (n+0+\varphi )$

$\varphi =0$

As ${\varphi }^{\prime }-\varphi =0\Rightarrow$ place difference $=0$

Option $-D$ is correct.