What is a plane polarised wave?

A plane polarised wave is a type of wave in which the vibration of particles occurs in only one plane, perpendicular to the direction of the wave’s motion.

In a plane polarised wave, all the vibrations move in one specific direction. Only transverse waves, such as light waves, can be plane polarised because their vibrations occur perpendicular to their travel path. Longitudinal waves, like sound, cannot be polarised since their vibrations are along the same direction as movement.

• Unpolarised wave: Vibrations occur in all directions.
• Plane polarised wave: Vibrations occur only in one fixed plane.
• Examples: Light reflected from glass or water becomes partially polarised.