11.1 Progressive waves Flashcards
What are the two types of waves produced by earthquakes?
primary or P-waves (longitudinal), secondary or S-waves (transverse) - both are types of a progressive wave that travel rapidly through parts of the Earth’s interior, they can cause significant damage to structures on the surface.
What is a progressive wave?
A progressive wave is an oscillation that travels through matter or in a vacuum. All progressive waves transfer energy from one place to another, but not matter. In other words, although the particles vibrate, they do not move alone the wave.
What is an example of a progressive wave and explain why it is.
Sound waves - when you hear someone talking to you, vibrations travel to your ears, but the air particles do not. Instead they vibrate in a plane parallel to the direction of energy transfer as the wave passes through the air.
Explain what happens when a progressive wave travels through a medium.
When a progressive wave travels through a medium, like air or water, the particles in the medium move from their original equilibrium position to a new position. The particles in the medium exert forces on each other. A displaced particle experiences a restoring force from its neighbours and it is pulled back to its original position.
What is a transverse wave?
The oscillations are perpendicular to the direction of the energy transfer - have peaks and troughs where the oscillating particles are at a maximum displacement from their equilibrium position.
Give examples of transverse waves.
- Water waves
- Electromagnetic waves
- Waves in strings
- S-waves produced by earthquakes
What is a longitudinal wave.
The oscillations are parallel to the direction of energy transfer.
Give examples of longitudinal waves.
- Sound waves
- P-waves produced by earthquakes
Describe how sound waves travel through air.
When sound waves travel through air, air particles are displaced and bounce off their neighbours. These collisions provide the restoring force. As the wave moves, regions of higher pressure and regions of lower pressure travel through the air, but no single air particle travels through the wave. Instead they oscillate about their equillibrium positions.
