Unit 7: The Form of Waves
Waves transfer energy without transferring matter. This unit looks at the physical form of waves: their shape, and the measurements we use to describe them.
01 Transverse and longitudinal waves
| Transverse | Longitudinal |
|---|---|
| Particles vibrate perpendicular (at 90°) to the direction the wave travels. Example: light, water waves, waves on a rope. | Particles vibrate parallel to (along) the direction the wave travels, forming compressions and rarefactions. Example: sound waves. |
02 Describing a wave
| Term | Meaning | Unit |
|---|---|---|
| Amplitude | Maximum distance a particle moves from its rest position | metre (m) |
| Wavelength (λ) | Distance from one point on a wave to the identical point on the next wave | metre (m) |
| Frequency (f) | Number of complete waves passing a point per second | hertz (Hz) |
| Period (T) | Time taken for one complete wave | second (s) |
03 The wave equation
wave speed (m/s) = frequency (Hz) × wavelength (m)
This equation connects how fast a wave travels to how often it repeats and how long each wave is.
V Key vocabulary
| Term | Meaning |
|---|---|
| Amplitude | The maximum displacement of a particle from its rest position. |
| Wavelength | The distance between two identical points on consecutive waves. |
| Frequency | The number of waves passing a fixed point each second, in hertz. |
| Transverse wave | A wave where vibration is perpendicular to the direction of travel. |
? Quick check
Try to answer before you tap. Answers are hidden underneath.
A wave has a frequency of 50 Hz and a wavelength of 2 m. Find its speed.
100 m/s (v = f × λ = 50 Hz × 2 m = 100 m/s).
Is sound a transverse or longitudinal wave? Explain.
Longitudinal — the air particles vibrate back and forth parallel to the direction the sound travels, creating compressions and rarefactions.
What happens to the amplitude of a wave as it loses energy?
The amplitude decreases, because amplitude is related to the energy the wave carries.