Property And Nature of Light



Polarisation

Polarisation of light is the direction of oscillation of the electric fields that make up a light wave. Ordinary unpolarised light, the wave vibrations (which occur at right-angles to the direction in which light waves travel) are randomly distributed around the axis of propagation, i.e, the directions of oscillations are in all directions.

Random Polarisation Diagram.  Flavio Spedalieri

Fig 2.0

Fig 2.0. This diagram shows the ordinary polarisation of light, the electro-magnetic waves propagate at random.

Polarised light, is light in which the oscillations of the electric field oscillate in either the horizontal or vertical planes (not to be confused with E and H planes). Light can also be circularly polarised. We will cover this in the laser tutorials in more detail.

Light can be polarised by the use of simple polarisation filters. When dealing with Lasers, more advanced methods are used to polarise light.

Polarisation of Light Diagram.  Flavio Spedalieri

Fig 2.1

Fig 2.1. This Diagram shows the details of light polarisation. A polarising filter work by subtracting the components of light orientated in a particular plane; if a second filter is placed in front of the first, with its transmission planes crossed ( at right-angles ) with the first filter, then NO light will be transmitted. A good example of this is in liquid crystal displays, which operate on the basis of polarised light.

In this section we will only cover the basics on polarisation. We will cover polarisation in greater details in the laser tutorials.