How can you produce a polarized light by a nicol prism & How light can be polarized by reflection .

polarized light by a nicol prism
polarized light by a nicol prism
Question : How light can be polarized by reflection .

Answer.Let us consider  an unpolarised nlight falls on a plane glass plate.Each light pulkse of the incident light has E vector that has the component along the plane of incidence called the component.Another component is perpendicular to the plane of incidence called the  component.There is a definite angle of incidence for which no  component is found in the reflected beam.This angle is called the polarizing anglep.Thus we have a reflected polarized beam of light.

Question : Explain double refraction of light ?

Answer : Light traveling through a crystal is divided into two parts.That is there are two refracted rays in the crystal.One obeys snell’s law.It is called ordinary ray(O-ray) and the other does not obey snell’s law.It is called extra ordinary ray(e-ray).This two rays are mutually perpendicularly polarized.In an oblique incidence e-ray and O-rat travel in two different directions with two different velocities.But in a normal incidence e-ray and O-ray travel in the same direction with two different velocities.This kind of refraction of light is called double refraction.

Question :How can you produce a polarized light by a nicol prism .

Answer : Nicol prism is an optical instrument that can produce a plane polarized light.It can also assure the existence of polarized light.It is made of calcite(CaCl2) crystal.Its length is three times its breath.Its edges from 680  and 1120 angles.It is cut along the blunt corner into two equal parts.

The two cut surface are joined together by a thin layer of Canada belsum.Canada belsum behaves like a denser medium for 0-rays rerer medium for e-rays.When a rays of unpolarised light falls on the prism surface it is divided into o-ray and e-ray within the prism metarial.These two rays fall on Canada belsum layer.These two rays fall on Canada belsum layer.o-ray is titally reflected and e-ray is transmitted without changing its direction.The transmitted beam is plane polarized.

polarized light by a nicol prism
Fig : polarized light by a nicol prism
Question: What is optical activity ?

Answer : The plane of polarization of a polarized light rotates while passing through soma sunstances.Such a property of a substance is called optical activity and the substance is called optically active substance.Sugar solution ia such a substance.

Question:What are the factors on which the rotation of the plane of polarization depends?

Answer : The rotation of the plane of polarization depends on the following factors:

(1)Density of the opticallt active substance.

(2)distance travelled through the substance.

(3)wave length .

(4)temperature

 

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