Make your own free website on Tripod.com
 
UNIT 6 : POLARIZATION


anilpangantiwar.tripod.com/physicsinfo.htm



Polarization, Polarisation by reflection,Brewster's law,Malus law,Double refraction,Nicol prism,Huygen's explanation of Double refraction in uniaxial crystals, Production & detection of plane, circularly and elliptically polarized light, quarter and half wave plate, Babinet compensator.


Edited by:- Dr. A. W. Pangantiwar

What do you understand by the term polarization of light? Describe the process of production of plane polarized light by reflection.

Calculate the thickness of double refracting plate capable of producing a path difference of one fourth of wavelength between extraordinary and ordinary waves.
Given - Wavelength = 5890 AU, R.I. of Ord. ray = 1.53, R.I. of Extra-Ord. ray = 1.54.

What is Babinet's compensator ? Explain how it can be used to analyse fully elliptically polarized light.

Explain the propagation of ordinary and extra-ordinary wavefront in a calcite crystal for normal incidence with optic axis :
(i) parallel to the direction of propagation and
(ii) normal to the direction of propagation.

Explain how a quarter wave plate functions to produce a circularly and elliptically polarized light..

What do you understand by polarization of light ? Distinguish between polarized and unpolarized light.

Discuss the production and detection of circularly polarized light.

Calculate the thickness of calcite quarter wave plate which would convert plane polarised light into circularly polarised light.
( Given : R.I. for ordinary wave = 1.658, R.I. for extraordinary wave = 1.486 and light used is of 5890 Angstrom ).

What do you understand by an ordinary ray and an extra-ordinary ray ? How do these differ from each other ?

Determine the path and the wavefronts of ordinary and extra-ordinary rays inside a double refracting crystal on the basis of Huygene's theory when the optic axis is inclined to the incident surface.

Unpolarized light falls on two polarizing sheets so oriented that no light is transmitted from the combination. If a third polarizing sheet is placed between them, can light be transmitted ? Explain.

Explain what do you understand by elliptically and circularly polarized light. How are they produced ?

We wish to use a plate of glass as a polarizer. What is it's polarizing angle ? ( R.I. = 1.5 for glass )

What is a quarter wave plate ? Deduce its thickness for a given wavelength in terms of its refractive indices.

An unpolarized light beam is incident on a polarizer. Show that the transmitted intensity will be half the incident intensity.

Linearly polarized light is incident on a polarizer sheet such that its electric vector makes an angle theta w.r.t. the transmission axis of the polarizer. What will be the transmitted intensity ?

What is half-wave plate ? Explain its action on plane polarized light incident on it with its electric vector making an angle theta with the optic axis of the half wave plate.

What are the optical devices required to produce circularly polarized light from unpolarized light ? Explain how they are used to produce circular and elliptical polarized light.

What is double refraction ?

Explain the propagation of ordinary and extraordinary wave fronts in a calcite crystal for normal incidence with optic axis :
(i) parallel to the direction of propagation and
(ii) normal to the direction of propagation.

Using Huygen's principle construct refracted beams and wavefronts in calcite when :
(i) Incident ray is normal to crystal surface, optic axis parallel to the crystal surface and lies in the plane of incidence.
(ii) Incident ray makes an angle theta with normal while optic axis is as above.

Unpolarized light falls on two polarising sheets placed one on the top of other. What must be the angle between their characteristic directions if intensity of transmitted light is one third of intensity of incident beam ?

Distinguish between :
(i) Ordinary ray and extraordinary ray
(ii) Positive and negative crystals.
(iii) Uniaxial and biaxial crystals.

It is desired to rotate the plane of polarization of a plane polarized light beam. How can it be achieved using a quartz crystal ? What should be the thickness of the quartz crystal used ?

Find out the state of polarization represented by the following equations :
Ex = Eo sin (wt - kz ) and
Ey = Eo cos (wt - kz).


 
REFERENCES
:-

1) http://physics.about.com/science/physics/library/dict/blglossary.htm

2) A Text Book of Optics by Subrahmanyam & Brijlal