(unpolarised light), optical radiation whose electromagnetic field strength changes direction rapidly and at random, all directions of oscillation perpendicular to the light rays being equally probable. Accordingly, when a beam of natural light is resolved into two linearly polarised beams in any two mutually perpendicular directions, two incoherent (see Coherence) components of the original beam arise with equal intensities. Being incoherent, the secondary beams do not interfere when they are brought together (see Interference of light). Many light sources (incandescent bodies, luminous gases) emit light close to natural light, but usually polarised to a small degree nonetheless. Direct sunlight is very close to natural light.