A wave is a disturbance that transfers energy from one point to another without transferring matter.
Wave Terms
| Term | Meaning |
|---|---|
| Wavelength (λ) | Distance between two successive crests (or compressions) |
| Frequency (f) | Number of complete waves per second (hertz, Hz) |
| Amplitude | Maximum displacement from the rest position |
| Period (T) | Time for one complete wave; T = 1/f |
The Wave Equation
Formula: v = fλ (speed = frequency × wavelength).
Types of Waves
- Transverse waves: the particles vibrate at right angles to the direction of the wave (e.g. light, water waves).
- Longitudinal waves: the particles vibrate along the direction of the wave (e.g. sound).
Sound
Sound is produced by vibrating objects and travels as a longitudinal wave. It needs a medium — sound cannot travel through a vacuum. Its speed in air is about 340 m/s.
- Echoes: sound reflected from a surface. Used in sonar and echo-sounding.
- Pitch depends on frequency; loudness depends on amplitude.
Worked Example
A wave has a frequency of 50 Hz and a wavelength of 6 m. Find its speed.
v = fλ = 50 × 6 = 300 m/s.
Summary
Waves transfer energy. The wave equation v = fλ links speed, frequency and wavelength. Sound is a longitudinal wave produced by vibration, needs a medium, and can be reflected as an echo.
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