Light and colours

In short: Visible light is electromagnetic radiation with wavelengths of about 400 to 700 nanometres. We see each wavelength as a different colour.

In more detail: White light contains all colours. A prism separates them because each colour is refracted by a different amount.

In detail

• Spectrum: From violet (short wave) through blue, green, yellow, orange to red (long wave).
• Object colours: An object looks red because it reflects red light and absorbs the other colours.
• Additive mixing: Screens mix red, green and blue (RGB). All three give white.
• Subtractive mixing: Printers use cyan, magenta, yellow and black (CMYK).
• Invisible light: Infrared and ultraviolet lie outside our range of vision (regenbogen-entstehung).