Dispersion

Intermediate

Different colours have different refractive indices.

n varies with wavelength (higher for blue), so white light splits into colours when refracted. It causes rainbows and chromatic aberration.

Worked example

Red n_glass = 1.51, violet 1.53.

Common mistake

Different from diffraction.

In more detail

Dispersion is the separation of white light into colours because the refractive index depends on wavelength. Violet bends more than red in glass.

Prisms and gratings split light into spectra for analysis.
Rainbows are formed by dispersion in water drops.
A prism spreads sunlight into a rainbow of colours, because each wavelength refracts by a slightly different angle.

Why is violet bent most?

Its refractive index is highest in most materials.

Do all materials disperse light?

Yes, to some extent, though the amount varies.

Which colour bends most?

Violet bends the most, since glass has a slightly higher refractive index for short wavelengths.