Physics – 3.2.3 Thin lenses | e-Consult

Violet light is dispersed more than red light because it has a shorter wavelength. The refractive index of a material describes how much light slows down when passing through it. The refractive index (n) is related to the wavelength (λ) of light by the equation: n = c/λ, where 'c' is the speed of light.

Since violet light has a shorter wavelength than red light, it travels slower in the glass prism (because of the lower speed of light in the glass). A lower speed of light in the glass means a greater change in direction (bending) as the light passes from air to glass and then back to air. Therefore, violet light is refracted more strongly than red light, leading to greater dispersion.