Waves (Edexcel GCSE Physics Combined Science): Revision Notes
Waves
Waves transfer energy from one place to another without transferring matter (no "stuff" moves with the wave). Instead, waves cause the particles of a medium to vibrate and pass energy along.
Particles and Waves:
- When waves travel through a medium (like air or water), the particles of that medium vibrate and transfer energy between each other.
- However, the particles do not move along with the wave; they just oscillate around a fixed point.
Types of Waves
Transverse Waves:
Vibrations in transverse waves are perpendicular to the direction the wave travels.
Examples of transverse waves:
- Electromagnetic waves (light, microwaves, etc.)
- S-waves (seismic waves in earthquakes)
- Ripples or waves on water
Key Features:
In transverse waves, particles move up and down while the wave moves horizontally.
Longitudinal Waves:
Vibrations in longitudinal waves are parallel to the direction the wave travels.
Examples of longitudinal waves:
- Sound waves
- P-waves (seismic waves during earthquakes)
Key Features:
Longitudinal waves cause compressions (where particles are close together) and rarefactions (where particles are spread out).
These compressions and rarefactions move in the same direction as the wave.
Key Wave Properties:
- Amplitude:
- The amplitude of a wave is the maximum displacement of a point on the wave from its rest position.
- In a transverse wave, it's the height from the middle (rest) to the crest (top) or trough (bottom).
- Wavelength:
- The wavelength is the distance between two corresponding points on adjacent waves (e.g., from crest to crest or compression to compression in longitudinal waves).
- Frequency:
- The frequency of a wave is the number of complete cycles (waves) that pass a given point per second.
- Measured in Hertz (Hz). For example, 1 Hz = 1 wave per second.
- Period:
- The period is the time it takes for one full cycle of the wave to pass a given point.
It is the inverse of the frequency:
Important Equations:
- Wave Speed:
This tells us how fast a wave is moving.
- Period of a Wave:
This shows how long one complete wave cycle takes.