What is meant by plane polarised light? What type of waves show the property of polarisation? Briefly discuss polarisation by reflection.

Plane polarised light refers to light waves that vibrate in a single plane, rather than in multiple directions. This type of light is created when unpolarised light, which vibrates in all directions, passes through a polarising filter. The filter allows only the waves aligned with its orientation to pass through, resulting in plane polarised light.

Waves That Exhibit Polarisation

Polarisation is a property primarily associated with transverse waves. The most common examples include:

• Light Waves: These are electromagnetic waves that can be polarised.
• Water Waves: Surface waves can also exhibit polarisation under certain conditions.
• Seismic Waves: Specifically, S-waves (shear waves) can be polarised as they move through the Earth.

Understanding Polarisation by Reflection

When light reflects off a surface, it can become polarised. This phenomenon occurs because the reflected light waves tend to align in a specific direction. The degree of polarisation depends on the angle of incidence, with maximum polarisation occurring at a specific angle known as Brewster's angle. At this angle, the reflected light is predominantly polarised in a plane parallel to the surface.

In summary, plane polarised light is a specific orientation of light waves, primarily seen in transverse waves, and polarisation can occur through reflection, particularly at certain angles.