Prism and light spectrum. Illustration showing colour separation (top half), which occurs to white light passing through a triangular prism. White light is formed by electromagnetic radiation of various wavelengths which correspond to the different colours. Violet light is deviated from the incoming path more than red light causing the colour bands to emerge from the prism. The two diagrams in the bottom half show absorption (black on coloured strip) and emission (coloured on black strip) lines which may be present in light spectra. These lines are caused by atoms which absorb or emit radiation at specific wavelengths.