Wave Properties & Types
Describe waves in terms of amplitude, wavelength, frequency, and wave speed; distinguish transverse waves (oscillation perpendicular to direction of travel) from longitudinal waves (oscillation parallel); and use the wave equation v = fλ
What a learner can do afterwards
- Labels a wave diagram with amplitude, wavelength, crest, and trough
- Distinguishes transverse and longitudinal waves and gives an example of each
- Uses v = fλ to calculate wave speed, frequency, or wavelength given the other two
- Explains what happens to wavelength if frequency increases while wave speed stays constant
The lesson
You already know a wave has crests and troughs. Now you can put numbers on those shapes. The amplitude is the wave's height: measure it from the middle resting line up to the crest. The wavelength is the wave's length: measure it from one crest to the next crest, or from one trough to the next trough.
A ripple in a pond rises 3 centimeters above calm water, so its amplitude is 3 cm. The distance from one crest to the next crest is 15 centimeters, so its wavelength is 15 cm.
Waves also move in different ways. In a transverse wave, the particles move up and down, perpendicular to the direction the wave travels. Light waves and waves on a rope work this way. In a longitudinal wave, the particles move back and forth, along the same line the wave travels. Sound waves move this way, squeezing and stretching the air as they go.
Two more measurements describe a wave. Frequency counts how many waves pass a point each second, measured in hertz (Hz). Wave speed tells you how fast the wave itself travels. These three ideas connect through the wave equation: speed equals frequency times wavelength, written v = fλ. A wave with a frequency of 5 Hz and a wavelength of 2 meters travels at 5 × 2 = 10 meters per second.
If a wave's speed stays constant and its frequency increases, the wavelength must get shorter. The two trade off so their product, the speed, doesn't change.
Amplitude is a wave's height, wavelength is its length, and v = fλ ties speed, frequency, and wavelength together.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.