Wave
A wave is a disturbance that transfers energy through a medium or through space without permanently displacing the medium itself. Waves are fundamental to how energy propagates in nature, from ocean ripples to light traveling across the universe. They are characterised by properties such as wavelength, frequency, amplitude, and speed, and underpin technologies ranging from radio communication to medical ultrasound.
Common Types of Waves and Their Properties
| Wave Type | Medium Required | Example | Speed (approx.) |
|---|---|---|---|
| Mechanical | Yes | Sound in air | 340 m/s |
| Electromagnetic | No | Visible light | 3 × 10⁸ m/s |
| Transverse | Yes / No | Light, water surface | Varies |
| Longitudinal | Yes | Sound | 340 m/s in air |
| Surface | Yes | Ocean waves | 1–30 m/s |
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Related Terms
Wavelength
Wavelength is the spatial distance between two consecutive points that are in the same phase of a wave, such as crest to crest or trough to trough. It is denoted by the Greek letter lambda (λ) and measured in metres. Wavelength is inversely related to frequency: higher-frequency waves have shorter wavelengths, which is why X-rays (short λ) are more energetic than radio waves (long λ).
Frequency
Frequency is the number of complete wave cycles that pass a fixed point per unit time, measured in hertz (Hz), where 1 Hz equals one cycle per second. It determines the pitch of a sound (higher frequency = higher pitch) and the colour of light (higher frequency = more energetic, bluer light). Frequency is inversely proportional to the wave period: f = 1/T.
Amplitude
Amplitude is the maximum displacement of a wave from its equilibrium (rest) position, representing the "height" of a wave. It is denoted by A and measured in metres for mechanical waves, or in volts, pascals, or other units depending on context. Amplitude is directly related to the energy carried by the wave: the greater the amplitude, the greater the energy, which is why louder sounds and brighter lights have larger amplitudes.
From Old English "wafian" (to wave the hand) and Proto-Germanic roots meaning to move back and forth. The physics usage solidified in the 17th century as scientists formalised the study of oscillatory motion.