CBSE NOTES CLASS 12 PHYSICS
CHAPTER 10 WAVE OPTICS
A light wave is an electromagnetic wave that travels through the vacuum of outer space. Light waves are produced by vibrating electric charges.
Ordinary light has electric vectors in all possible directions in a plane perpendicular to the direction of propagation of light. Hence it is called unpolarised light.
It can be considered a combination of vertical and horizontal components. Average of half its vibrations are in a horizontal plane and half of its vibrations are in a vertical plane.
The phenomenon of restructuring of electric vectors of light into a single direction is called polarisation.
When ordinary light is passed through a tourmaline, calcite or quartz crystal the transmitted light has electric vectors in a particular direction parallel to the axis of crystal. This light is called plane polarised light.
A plane containing the vibrations of polarised light is called plane of vibration.
A plane perpendicular to the plane of vibration is called plane of polarisation.
Polarisation can take place only in transverse waves.