How Does One Demonstrate, Using a Suitable Diagram, that Unpolarised Light When Passed Through a Polaroid Gets Polarised? - Physics


How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a Polaroid gets polarised?



The phenomenon of restricting the vibration of light (electric vector) in a particular direction perpendicular to the direction of the wave propagation is called polarisation of light.

When unpolarised light is passed through a Polaroid, only those vibrations of light pass through the crystal, which are parallel to the axis of the crystal (AB). All other vibrations are absorbed and that is why intensity of the emerging light is reduced.

The plane ABCD in which the vibrations of the polarised light are confined is called the plane of vibration. The plane KLMN that is perpendicular to the plane of vibration is defined as the plane of polarisation

Concept: Polarisation
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2013-2014 (March) Delhi Set 1


If the polarising angle for a given medium is 60°, then the refractive index of the medium is.................

What is a Polaroid?

With the help of neat diagram, explain how non-polar dielectric material is polarised in external electric field of increasing intensity. Define polarisation in dielectrics.

Draw a neat labelled diagram showing the plane of vibration and plane of polarisation for polarised light.

For a glass plate as a polariser with refractive index 1.633, calculate the angle of incidence at which light is polarised.

If the critical angle of a medium is sin-1(3/5), find the polarising angle.

A beam of unpolarised light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarised, when μ = tan iB, where μ is the refractive index of glass with respect to air and iB is the Brewster's angle.

Show, with the help of a diagram, how unpolarised sunlight gets polarised due to scattering.

The refractive indices of glass and water w.r.t. air are 3/2 and 4/3 respectively. Determine the refractive index of glass w.r.t. water.

The refractive indices of water for red and violet colours are 1.325 and 1.334 respectively.
Find the difference between the velocities of rays for these two colours in water. (c = 3 × 108 m/s)

A ray of light passes from a vacuum to a medium of refractive index (μ). The angle of
incidence is found to be twice the angle of refraction. The angle of incidence is _______.

A) `cos^(-1)(mu/2)`

B) cos−1(μ)

C)  `2 cos^(-1) (mu/2)`

D) `2 sin^(-1) (mu/2)`

Unpolarised light is passed through a polaroid P1. When this polarised beam passes through another polaroid P2 and if the pass axis of P2 makes angle θ with the pass axis of P1, then write the expression for the polarised beam passing through P2. Draw a plot showing the variation of intensity when θ varies from 0 to 2π.

What is the value of refractive index of a medium of polarising angle 60°?

State two uses of Polaroid.

The glass plate of refractive index 1.732 is to be used as a polarizer, its polarising angle is _______.

With the help of an experiment, state how will you identify whether a given beam of light is polarised or unpolarized?

State any two methods by which ordinary light can be polarised

What does a polaroid consist of? How does it produce a linearly polarised light?

Unpolarised light is incident on a polaroid. How would the intensity of transmitted light change when the polaroid is rotated?

Which of the following properties shows that light is a transverse wave?

A beam of light is incident at the polarizing angle of 35° on a certain glass plate. The refractive index of the glass plate is : 

Green light is incident at the polarising angle on a certain transparent medium. The angle of refraction is 30° . Find
(i) polarising angle, and
(ii) refractive index of the medium.

A ray of light is incident on a transparent medium at a polarizing angle. What is the angle between the reflected ray and the refracted ray?

What is the difference between polarised light and unpolarised light? 

A ray of ordinary light is travelling in air. It is incident on air glass pair at a polarising angle of 56°. Find the angle of refraction in glass.

Explain how an unpolarised light gets polarised when incident on the interface separating the two transparent media.

Light transmitted by Nicol prism is ______.

What is polarisation?

What is a polariser?

What is a analyser?

What is plane polarised light?

What is partially polarised light?

State and obtain Malus’ law.

State Brewster’s law.

What is the angle of polarisation and obtain the equation for an angle of polarisation?

What is double refraction?

Mention the types of optically active crystals with example.

Discuss about Nicol prism.

How is polarisation of light obtained by scattering of light?

What is normal focusing?

An unpolarised light of intensity 32 Wm-2 passes through three Polaroids such that the axes of the first and the last Polaroids are at 90°. What is the angle between the axes of the first and middle Polaroids so that the emerging light has an intensity of only 3 Wm-2?

A plane mirror produces a magnification of

Polarisation of light is the only phenomenon that establishes ______.

Which of the following phenomena is not common to sound and light waves?

Can reflection result in plane polarised light if the light is incident on the interface from the side with higher refractive index?

For the same objective, find the ratio of the least separation between two points to be distinguished by a microscope for light of 5000 Å and electrons accelerated through 100 V used as the illuminating substance.

To ensure almost 100 per cent transmissivity, photographic lenses are often coated with a thin layer of dielectric material. The refractive index of this material is intermediated between that of air and glass (which makes the optical element of the lens). A typically used dielectric film is MgF2 (n = 1.38). What should the thickness of the film be so that at the center of the visible spectrum (5500 Å) there is maximum transmission.

An unpolarized light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by 30° in clockwise direction, the intensity of emerging light will be ______ Lumens.

A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just 10% of the original intensity. Assuming that the polarizer - analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero, is ______.


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