. . Wave theory Christian Huygens ( ) proposed the wave theory to explain the propagation of light through a medium. According to him, light is a disturbance from a source travels that as longitudinal mechanical waves through the ether medium (that was presumed to pervade all space) as mechanical wave requires a medium for its propagation.
The wave theory could successfully explain phenomena of reflection, refraction, interference and diffraction of light. Later, the existence of ether in all space was proved to be wrong. Hence, this theory could not explain the propagation of light through vacuum. The phenomenon of polarisation could not be explained by this theory as it is the property of only transverse waves.
. . Electromagnetic wave theory Maxwell ( ) proved that light is an electromagnetic wave which is transverse in nature carrying electromagnetic energy. He could also show that no medium is necessary for the propagation of electromagnetic waves.
All the phenomenon of light could be successfully explained by this theory. Nevertheless, the interaction phenomenon of light with matter like photoelectric effect and Compton effect could not be explained by this theory. . .
Quantum theory Albert Einstein ( ), endorsing the views of Max Plank ( ), was able to explain photoelectric effect (discussed in Unit ) in which light interacts with matter as photons to eject the electrons. A photon is a discrete packet of energy. Each photon has energy E of, E = hv ( . ) Where, h is Plank’s constant ( h = .
× – Js) and v is frequency of electromagnetic wave. As light has both wave as well as particle nature it is said to have dual nature. It is concluded that light propagates as a wave and interacts with matter as a particle. WAVE NATURE OF LIGHT Light is a transverse, electromagnetic wave.
The wave nature of light was first demonstrated through experiments like interference and diffraction. The transverse nature of light is demonstrated in polarization. Like all electromagnetic waves, light can travel through vacuum. .
. Wave optics Wave optics deals with the wave characteristics of light. Even the law of reflection