The wave-particle duality principle of quantum physics holds that light exhibit the behaviors of both waves and particles (energy particles called photons), depending upon the circumstances of the experiment.

The length of a wave, meaning the distance measured in the direction of the wave from any given point to the next point in the same phase, as from crest to crest. Humans can perceive different electromagnetic waves of the visible light as different colours, e.g. the longest wavelength corresponds to red colour while the shortest one to violet.

Light having the different colors (red, orange, yellow, green, blue, indigo and violet) in the same proportion as in the light coming directly from the sun, without having been decomposed, as by passing through a prism.