Waves & Sound Reference
Wave Equation
The wave speed equation connects frequency, wavelength, and speed:
v = f × λ
where v = wave speed (m/s), f = frequency (Hz), λ = wavelength (m).
Wave Types
- Transverse waves: particles move perpendicular to wave direction (light, water surface).
- Longitudinal waves: particles move parallel to wave direction (sound in air).
Wave Properties
- Wavelength (λ): distance between successive crests (meters).
- Frequency (f): cycles per second (Hertz, Hz).
- Period (T): time for one cycle; T = 1/f.
- Amplitude (A): maximum displacement from equilibrium — related to energy.
Sound Intensity & Decibels
Sound intensity level (dB) = 10 log10(I / I₀), where I₀ = 10⁻¹² W/m² (threshold of hearing).
Each 10 dB increase represents a 10× increase in intensity.
Standing Waves & Resonance
Standing waves form when waves of the same frequency reflect and interfere. Nodes are points of zero displacement; antinodes are maximum displacement points. Resonance occurs when a driving frequency matches the natural frequency of a system.
The Doppler Effect
When a wave source moves toward an observer, the observer hears a higher frequency. When moving away, lower frequency. This is the Doppler effect, and it applies to sound, light, and all wave types.