Wave Properties
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by Natalie Dyer
| 7 Questions
Note from the author:
Basic properties of transverse and longitudinal waves
Information and graphics adapted from https://www.acs.psu.edu/drussell/demos/waves/wavemotion.html

Longitudinal Waves

In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation below shows a one-dimensional longitudinal plane wave propagating (moving) down a tube. The particles do not move down the tube with the wave; they simply oscillate back and forth about their individual equilibrium positions. Pick a single particle and watch its motion. The wave is seen as the motion of the compressed region (ie, it is a pressure wave), which moves from left to right.


zoom_in

The second animation below shows the difference between the oscillatory (back-and-forth) motion of individual particles and the propagation (movement) of the wave through the medium. The animation also identifies the regions of compression and rarefaction.


zoom_in

The P waves (Primary waves) in an earthquake are examples of Longitudinal waves. The P waves travel with the fastest velocity and are the first to arrive.

To see a animations of spherical longitudinal waves check out:
  • Sound Radiation from Simple Sources
  • Radiation from Cylindrical Sources
1
1
Look at the animations of longitudinal waves above. What happens to the particles of matter (red dot) as the waves move through them?
They do not move at all.
They move up and down, but come back to their original position.
They move side to side, but come back to their original position.
They travel down the screen with the wave and do not come back to their original position.
2
1
The P-waves move fastest and arrive first. (This is why they're called Primary Waves.)
True
False
3
1
In a longitudinal wave the particles move ______________________ to the direction of the wave.
Parallel (in the same direction)
Perpendicular (across the wave's direction)

Transverse Waves

In a transverse wave the particle displacement is perpendicular to the direction of wave propagation. The animation below shows a one-dimensional transverse plane wave propagating from left to right. The particles do not move along with the wave; they simply oscillate (move) up and down about their individual equilibrium positions as the wave passes by. Pick a single particle and watch its motion.

zoom_in

The S waves (Secondary waves) in an earthquake are examples of Transverse waves. S waves propagate (move) with a velocity slower than P waves, arriving several seconds later.

4
1
Look at the animation of the transverse wave above. What happens to the particles of matter (red dot) as the waves move through them?
They do not move at all.
They move up and down, but come back to their original position.
They move side to side, but come back to their original position.
They travel down the screen with the wave and do not come back to their original position.
5
1
In a transverse wave the particles move ______________________ to the direction of the wave.
Parallel (in the same direction)
Perpendicular (opposite)
6
1
The S-waves move fastest and arrive first. (This is why they're called Secondary Waves.)
True
False

Water Waves

Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases. The animation at right shows a water wave travelling from left to right in a region where the depth of the water is greater than the wavelength of the waves. I have identified two particles in orange to show that each particle indeed travels in a clockwise circle as the wave passes.

zoom_in

7
1
Look at the animation of the water wave above. If you were on a surf board in the ocean, how would you move in relation to the wave?
I would not move at all.
I would move up and down, but come back to my original position.
I would move side to side, but come back to my original position.
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