Transverse and longitudinal waves
Transverse and longitudinal waves
Waves transfer energy from one place to another without transferring matter.
the oscillations (vibrations) are at right angles to the direction the energy travels. Examples: ripples on water, waves on a string, light and all other electromagnetic waves, and seismic S-waves.
the oscillations are parallel to the direction the energy travels. They have , where particles are squashed close together, and , where they are spread out. Examples: sound waves and seismic P-waves.
Common mistake
The wave moves on, but the material doesn't. A cork on a pond bobs up and down as ripples pass; it doesn't travel along with them. Air doesn't travel from a speaker to your ear: its particles just vibrate back and forth.
Key terms
Describing a wave
- the of a point on the wave from its undisturbed (rest) position.
- the distance from a point on one wave to the same point on the next wave, such as crest to crest.
- the number of waves passing a point each second, in . 1 Hz is one wave per second.
- the time for one complete wave to pass a point, in seconds.
This equation is on the equation sheet:
period = 1 ÷ frequency, or T = 1/f
Example: find the period of a wave with a frequency of 50 Hz.
- T = 1/f = 1 ÷ 50
- T = 0.02 s