Video Transcript
A longitudinal wave consists of
individual particles that might possibly move in the directions A, B, C, and D
shown in the diagram. Which of the following
directions can the yellow particle shown in the diagram move in as the wave
travels to the right?
Okay, so in this question,
we’ve got these blue particles that make up some medium. And this medium is carrying
along a longitudinal wave travelling from the left to right. Additionally, we’ve been asked
to consider this yellow particle in particular. We need to work out which of
the directions A, B, C, and D can this yellow particle move in. Now, to answer this question,
we need to recall that, for longitudinal waves, the direction of oscillation is
parallel to the direction of wave propagation, where the direction of
oscillation is referring to the direction in which these particles can move as
the wave passes through the medium made up by these particular particles. And the direction of wave
propagation is simply the direction in which the wave is moving, in this case
left to right.
So if the wave is moving left
to right and the particles can move in any direction parallel to this, then the
particles themselves could move left to right or right to left. In other words then, they can
move in the direction B or in the direction D. Now, an easy way to remember
that for longitudinal waves, those are the possible directions of oscillation,
is to remember that, in a longitudinal wave, the particles move along the same
direction as the wave itself. And hence, we’ve found the
answer to our question. The directions in which the
yellow particle can move as the wave travels to the right is direction B and
direction D.
