Home / Topics / Waves & Sound
Dispersion
Advanced
Different wavelengths travel at different speeds.
In a dispersive medium wave speed depends on frequency, so a pulse spreads. Glass prisms disperse white light; optical fibres broaden pulses.
Rainbow colours.
Non-dispersive: sound in air at normal frequencies.
In more detail
Dispersion occurs when the wave speed depends on frequency, so different frequencies separate over distance. Prisms split white light into colours by dispersion.
Real-world uses
- Prisms and diffraction gratings separate light into spectra.
- Optical fibres must control dispersion to carry signals over long distances.
- A prism spreads white light into colours because different wavelengths travel at different speeds in glass.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why does a prism split light?
Because the refractive index depends on wavelength, so each colour bends differently.
Which colours bend most?
Violet bends more than red in typical glass.
Which colour bends most in a prism?
Violet bends most, because it has the shortest wavelength and the largest refractive index in glass.
Related topics in Waves & Sound
Mach number · Energy transport in waves · Wave packets and group velocity · Waves in water · Tsunami and shallow water waves · Seismic waves