7.2.1Waves and superposition
Transverse and Longitudinal Waves
5 min read 7 parts Lesson 8 of 21 1 quiz Virtual lab
Lesson summary
7.2.1 Transverse and Longitudinal Waves — AS PHYSICS 9702 notes: Define transverse and longitudinal waves, compare their properties and interpret their graphs.Particles — in mechanical waves, particles oscillate about fixed points.Two types — transverse and longitudinal.Deciding …
- Deciding the type
- Definition
- Polarisation
- Compression
- Rarefaction
- Wavelength
Section 1 of 7Mechanical waves
Mechanical waves
Particles
- Particles in mechanical waves, particles oscillate about fixed points.
Two types
- Two types transverse and longitudinal.
Deciding the type
- Deciding the type compare the direction of the oscillations with the direction the wave travels.
Section 2 of 7Transverse waves
Transverse waves
Definition
- Definition a wave in which the particles oscillate perpendicular to the direction of motion and energy transfer.
Features
- Features areas of peaks and troughs.
Examples
- Examples electromagnetic waves such as radio, visible light and UV, and vibrations on a guitar string.
Vacuum
- Vacuum they do not need particles to propagate, so they can travel through a vacuum.
Polarisation
- Polarisation transverse waves can be polarised.
Section 3 of 7Longitudinal waves
Definition
- Definition a wave in which the particles oscillate parallel to the direction of motion and energy transfer.
Compression
- Compression an area of high pressure where the particles are closer together.
Rarefaction
- Rarefaction an area of low pressure where the particles are further apart.
Example
- Example sound waves.
Vacuum
- Vacuum they need particles to propagate, so they cannot travel through a vacuum.
Polarisation
- Polarisation longitudinal waves cannot be polarised.
Wavelength
- Wavelength the distance between two successive compressions or two successive rarefactions.
Section 4 of 7Comparing the two wave types
| Feature | Transverse | Longitudinal |
|---|---|---|
| Oscillation direction | Perpendicular to direction of energy transfer | Parallel to direction of energy transfer |
| Features | Peaks and troughs | Compressions and rarefactions |
| Travel through a vacuum | Yes | No |
| Can be polarised | Yes | No |
| Examples | EM waves, guitar string | Sound |
Section 5 of 7Graphs of waves
Same graph
- Same graph transverse and longitudinal waves can be represented graphically in the same way.
Meaning of displacement
- Meaning of displacement it is the main difference.
- For a transverse wave, displacement is perpendicular to the direction of propagation.
- For a longitudinal wave, displacement is parallel to the direction of propagation.
Other quantities
- Other quantities displacement can be replaced by velocity or acceleration on the y-axis.
Time graph
- Time graph a displacement–time graph of one particle could be either wave type, so read the question for the direction of travel.
Wave properties
- Wave properties amplitude, wavelength, period and frequency apply to both types.
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Transverse wave | Wave in which particles oscillate perpendicular to the direction of motion and energy transfer. |
| Longitudinal wave | Wave in which particles oscillate parallel to the direction of motion and energy transfer. |
| Compression | Region of a longitudinal wave where particles are closer together, at high pressure. |
| Rarefaction | Region of a longitudinal wave where particles are further apart, at low pressure. |
| Mechanical wave | Wave in which particles of a medium oscillate about fixed points. |
Section 7 of 7Exam technique
1
Saying a longitudinal wave has crests and troughs — it has compressions and rarefactions.
2
Thinking sound can travel through a vacuum — longitudinal waves need a medium.
3
Deciding the wave type from a displacement–time graph alone — the graph cannot show it.
4
Mixing up the definitions — transverse is perpendicular, longitudinal is parallel.