Polarisation of Light - SS1 Physics Lesson Note

Polarisation of light refers to the orientation of the electric field vector associated with a light wave. Unlike ordinary light, which consists of electromagnetic waves oscillating in all possible directions perpendicular to the direction of propagation, polarized light oscillates in a specific plane.

Here are the key points regarding the polarisation of light:

1. Transverse Nature of Light: Light is an electromagnetic wave, and its electric and magnetic fields oscillate perpendicular to the direction of propagation. This transverse nature allows light to exhibit polarisation.

2. Polarisation States: Polarised light can be classified into different polarisation states based on the orientation of the electric field vector. The most common polarisation states are linear polarisation, circular polarisation, and elliptical polarisation.

3. Linear Polarisation: In linearly polarised light, the electric field oscillates in a specific direction along a straight line. The direction of polarisation is typically represented by an angle with respect to a reference axis. Linear polarisation can be horizontal, vertical, or at any angle in between.

4. Polarisation Filters: Polarisation filters are optical devices that can selectively transmit light waves of a specific polarisation state while blocking light waves of other polarisation states. They are commonly used to manipulate and analyse polarised light.

5. Production of Polarised Light: Polarised light can be produced through various methods. One common method is by passing unpolarised light through a polarising filter, which selectively transmits light waves oscillating in a specific direction. Other methods include reflection, scattering, and birefringence in certain materials.

6. Polarisation and Reflection: When unpolarised light reflects off a non-metallic surface, such as glass or water, the reflected light becomes partially polarised. This polarisation occurs because the reflected light tends to be polarised in the plane parallel to the surface.

7. Applications of Polarised Light: Polarised light has numerous applications in various fields. Some examples include 3D movie technology, liquid crystal displays (LCDs), polarised sunglasses to reduce glare, and optical microscopy techniques such as polarised light microscopy.

8. Analysing Polarised Light: Polarised light can be analysed using tools such as polarisers, waveplates, and optical devices like polarimeters. These instruments allow scientists to determine the polarisation state, measure the degree of polarisation, and study the interaction of polarised light with different materials.

Understanding polarisation is important in fields such as optics, photonics, telecommunications, and materials science, as it provides insights into the behaviour of light and enables the development of various optical devices and technologies.