Name: Nature of Electromagnetic Waves
Uploaded: 2019-07-19
Duration: 5 min 57 s
Description: Have you ever wondered why light doesn’t push you, the way wind or water do? Or does it? Watch this video to learn how light exerts a force on us.

Question

What is meant by plane-polarised light? What type of waves shows the property of polarisation? Give a method for producing a beam of plane-polarised light. Show how you will detect the presence of plane-polarised light. Give one practical use of polarised light.

Accepted Answer

Light is an electromagnetic wave whose light vector is oscillating all direction perpendicular to the direction of propagation. This is called unpolarized light. If this light is passed through special crystals then the emerging light will have its vibrations in one particular direction only. as shown in the figure., This light is called the plane polarised light and the phenomenon is called polarisation.

The phenomenon of polarization can only show by a transverse wave. As longitudinal waves have their oscillations (compression and rarefaction on in the direction of propagation, in fact, this phenomenon has demonstrated that the light is a transverse wave.

Production of plane polarised light.

One of the most common way to get plane polarise light is through a Polaroid

Polaroid is a crystal of quinine idosulphate cut along its pass axis. If such crystal is placed in the way of unpolarized light, it will allow to pass only those vibrations which have their plane of vibration in the direction of its pass axis and thus the emerging light will have its vibrations only in one direction and will be plane polarised.

Detection of plane polarised light The plane polarised light can be detected using another Polaroid (called analyser). If a polarised light is observed through analyser, and the analyser is rotated around the axis of light propagation then the intensity of the light will vary depending upon wether the pass axis of the analyser in the plane of the vibration of the polarised light or inclined to it as shown in the figure.

Polaroids are used to reduce glare from the head lights of the incoming vehicle. A thin film of Polaroid on the windscreen of the vehicle will filter out the horizontal component of incoming light and the driver can avoid the glare of head light og incoming vehicle.

What is meant by plane-polarised light? What type of waves shows the property of polarisation? Give a method for producing a beam of plane-polarised light. Show how you will detect the presence of plane-polarised light. Give one practical use of polarised light.

Important Questions on Polarisation of Light

Learn and Prepare for any exam you want !