Question

The points moving upward is/are

• A. a
• B. c
• C. f
• D. g

Answer 1

Answer: (A), (D)

g
a

Particle velocity at a given position and time =negative of the product of wave velocity and the slope at that point i.e.
$v_{particle}=-v\times \frac{dy}{dx}$

$v_{particle}=-v\times$slope at that point.....................1
where v is wave velocity
Since the wave is moving in negative x direction wave velocity is negative.
For the particle to move upward the particle velocity should be positive.
and for the particle velocity to be positive the slope at the points should be positive because wave velocity is negative. using equation 1
From figure we can say that the slope is positive at the points a , g , h.
Hence option A and D are correct