Equilateral prisms achieve spectral dispersion by utilizing light of different wavelengths that have different refractive indices when passing through the prism material. When white light enters a prism, due to the different refractive angles of light of different colors (i.e. different wavelengths), they will be dispersed and form a spectrum after passing through the prism. The effect is similar to that of a diffraction grating, and a dispersive prism is more concise and stable.