Concept of unpolarised light:

i. According to Maxwell, light is an electromagnetic wave.

ii. Electromagnetic wave consists of electric and magnetic field vectors which vibrate perpendicular to each other and both are also perpendicular to the direction of propagation of the light wave.

iii. The phenomenon concerning light are described by only the electric vector i.e., light is represented by the electric field vector\((\overrightarrow E)\)

iv. In an unpolarised or ordinary light, the electric field vector \(\overrightarrow E\) is always perpendicular to the direction of propagation of light.

v. There are infinite number of directions perpendicular to the direction of propagation of light. So the electric field vector may be along any one of these directions.

vi. For example, if the light propagates along the X-axis, the electric field vector may be along Y-axis, or along Z-axis or along any direction in Y-Z plane and at any instant, electric vector can be resolved into two mutually perpendicular components.