What is Light?
Lights and its properties
For thousands of years many scientists groped in dark to understand the true nature of light. The ancient Greeks belived that light consisted of rays of matter given out by whatever object was being looked at. Plato and his followers belived that it was a mixture of different matters coming from the sun. But in the 11th century it was Alhazen the Arabic scientist who was the first to propund the theory that light could be given out by all luminous object. In the 17th century the British scientist Sir Isaac Newton put forward the corpuscular theory of light. According to this theory light travels in the form of corpuscles in stright lines through an imaginary medium called ether. In order to explain the transverse nature of light James Clark Maxwell developed the electromagnetic wave theory.
According to this theory light travels in the form of electromagnetic waves both electric and magnetic fields are perpendicular to the direction of propagation, ie. they are transverse electromagnetic waves. To explain the photoelectric effect max Planck put fourth the quantum theory of light in 1900. He suggested that light is given off in the form of photons. All electromagnetic radiations are given out in the photons. The quanta behave both like particles and waves of energy. When the quanta of sufficient energy fall on certain substances they give off electrons from their atoms. This is called photoelectric effect which means production of electricity by light. Today almost all the physical phenomena of optics are explained on the basis of quantum theory of light as explained above ie. light is made up of waves and particles both.