मराठी

Polarization

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Estimated time: 9 minutes
  • Polarization by Reflection: Brewster’s Law
  • Polarization by Scattering
Maharashtra State Board: Class 11

Definition: Polarisation of Light

The phenomenon of restriction of the vibration of light waves in a particular plane perpendicular to the direction of wave motion is called polarisation of light.

Maharashtra State Board: Class 11

Definition: Transverse Wave

When the displacement of the particle is perpendicular to the direction of propagation of the wave, then it is said to be transverse wave.

Maharashtra State Board: Class 11

Definition: Linearly Polarised Wave (Plane Polarised Wave)

The wave in which the vibration of electric field vectors are confined in one plane and parallel to one unique direction is called linearly polarised wave; it is also referred to as plane polarised wave.

Maharashtra State Board: Class 11

Definition: Unpolarised Wave

When the plane of vibration of a wave is changed randomly in very short intervals of time, such waves are called unpolarised waves.

Maharashtra State Board: Class 11

Definition: Polaroid

A thin film of ultramicroscopic crystals used to produce plane polarised light is called a polaroid.

Maharashtra State Board: Class 11

Law: Malus' Law

Statement: When plane polarised light is incident on an analyser, the resultant intensity of light transmitted from the analyser varies directly as the square of the cosine of the angle between the plane of transmission axis of the analyser and polariser.

Formula:

I = I0 cos⁡2 θ

Where:

  • I0 = intensity of plane polarised light
  • I = intensity of transmitted light from the analyser
  • θ = angle between the axis of the polariser and the analyser
Maharashtra State Board: Class 11

Law: Brewster's Law

Statement: When unpolarised light is incident at polarising angle iB on an interface separating air from a medium of refractive index μμ, then the reflected light is plane polarised (perpendicular to the plane of incidence), provided:

μ = tan ⁡iB

Additional condition at polarising angle:

iB + r = \[\frac {π}{2}\]

i.e., the reflected plane polarised light is at right angles to the refracted light.

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