1. Properties of Waves
9.2

2. The Parts of a Wave
Waves can differ in how much energy they carry and in how fast they travel.

3. The Parts of a Transverse Wave
A transverse wave has alternating high points.

4. The crest is the highest point on a wave.

5. The trough is the valley between two waves, is the lowest point.

6. A wavelength is the distance between one point on a wave and the nearest point just like it.
For transverse waves, the wavelength is the distance from crest to crest or trough to trough.

7. The amplitude is the peak (greatest) value (either positive or negative) of a wave. The distance from the undisturbed level to the trough or crest.

8. The Parts of a Longitudinal Wave
A longitudinal wave has no crests and troughs.
Longitudinal waves are also known as compressional waves.

9. The compression is the part of the compressional wave where the particles are crowded together or denser.

10. The rarefaction is the part of the compressional wave where the particles are spread apart.
less dense region

11. The wavelength is the distance from compression to compression or rarefaction to rarefaction in a longitudinal wave.

12. Amplitude of Longitudinal Waves
The closer the coils are in a compression, the farther apart they are in a rarefaction.

13. So the less dense the medium is at the rarefactions, the more energy the wave carries.

14. Frequency and Period Frequency is expressed in hertz (Hz).
The frequency of a wave is the number of wavelengths that pass a fixed point each second.
You can find the frequency of a transverse wave by counting the number of crests or troughs that pass by a point each second.
Frequency is expressed in hertz (Hz).

15. Period has units of seconds.
The period of a wave is the amount of time it takes one wavelength to pass a point.
As the frequency of a wave increases, the period decreases.
Period has units of seconds.

16. Wavelength is Related to Frequency
As frequency increases, wavelength decreases.
The frequency of a wave is always equal to the rate of vibration of the source that creates it.
If you move the rope down, up, and back down in 1 s, the frequency of the wave you generate is 1 Hz.

17. The speed of a wave depends on the medium it is traveling through.
Ex: sound waves – faster through liquids and solids than gases
light waves – slow in liquids and solids than gases or a vacuum
sound waves – faster through warmer materials than cooler materials

18. Calculating Wave Speed
You can calculate the speed of a wave represented by λ by multiplying its frequency times its wavelength.