Two complimentary theories have been proposed to explain how light behaves and the form by which it travels.
1. Particle theory: Light consists of a stream of small particles, because it travels in
straight lines at great speeds is reflected from mirrors in a predictable way.
2. Wave theory: Light is a wave, because it undergoes diffraction and interference (Young's
double–slit experiment).
The scientific study of the behavior of light covers reflection, refraction, polarization, diffraction of light as it passes by the edge of an opaque object and interference patterns resulting from diffraction.
Louis de Broglie showed that moving particles have certain wave like properties that govern their motion and that there exists complementarities between particles and waves known as wave–particle duality. Thus the quantum theory of light has successfully explained all aspects of the behavior of light's dual nature.
If a photon of light is absorbed by the electron, the electron gains potential energy and raises to a higher energy level. The electron's higher position is only momentary as a photon of light is emitted by the electron at the same instant. The electron loses potential energy returns to a lower level as it emits radiant energy.