What ispolarization inChemistry

Polarization of Light is a property applying to transverse waves that specify the geometrical orientation of the oscillations. Light is an electromagnetic wave in which electric and magnetic field vectors are sinusoidally perpendicular to each other as well as they are perpendicular to the direction of propagation of light waves.

When the electric field vectors are restricted to a single plane by filtration, then the light is said to be polarized with respect to the direction of propagation and it propagates in a single plane. In this article, we are going to learn about the polarization of light, brewster’s law, double refraction, polarization by scattering. Let’s understand the Physics (Optics) phenomenon of unpolarized light first.

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For calcite, one of the two rays does indeed obey Snell’s Law (angle of incidence is equal to the angle of refraction), this ray is called the ordinary ray (or O-ray). The other ray (and any ray that does not obey Snell’s Law) is an extraordinary ray (or E-ray). For normal incidence (a Snell’s law angle of 0°), the two planes of polarization are also perpendicular to the plane of incidence.

This is the reason the sky scatters more blue light than red because of the natural frequency of molecules in our atmosphere.

A polarimeter is an instrument used to determine the angle through which plane-polarized light has been rotated by a given sample.

Thus using Brewster’s law, we can conclude that polarizing angle depends on frequency of incident ray i.e., colour of incident ray hence polarizing angle will be different for different colour.

The specific rotation is a characteristic property of a certain substance and is the standard measurement for the optical rotation of that substance.

Optical activity is the ability of a substance to rotate the plane of polarization of a beam of light that passed through it.

What ispolarization ofwavesin Physics

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What is plane polarizedlight inChemistry

Polarizationby reflection

For monoclinic or tetragonal crystals, we get the above result i.e., One O-ray and one e-ray can be observed. Whereas for orthorhombic, monoclinic, and triclinic crystals, there will be two E-rays

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Now if we rotate second polarizer in such a way that it becomes perpendicular to first one, in this case as plane polarized light passes through second polarizer it will get eliminated since second polarizer won’t allow it to pass and hence it is called analyzer which is used to determine the plane of polarization as shown below

When light wave propagates it consists of vibration of electric field in all possible direction, which are perpendicular to its direction of propagation and such light waves are said to be unpolarized light.

The optical rotation is the angle through which the plane of polarization is rotated when polarized light is passed through a layer of a liquid.

Now as this unpolarized light passes through the polarizer, it will polarize the light in either vertical or horizontal direction. This polarized light when again passed through a polarizer there can be two possible outcomes.

Polarisation meaningin Physics

If the plane of vibration of both polarizers are parallel to each other in such polarized light from the first polarizer can easily pass through the second polarizer as shown below.

Polarization of lightnotes PDF

Polarization by scattering is generally observed in liquid or gas randomness in motion of atoms. However, in perfect crystals we don’t see as good results as fluids.

Suppose if a pencil mark is drawn upon a sheet of paper and then covered with a piece of glass, only one image will be seen. But if the same paper is covered with a piece of calcite and the crystal is oriented in a specific direction then two marks will become visible. This is because a refracted beam acquires some degree of polarization. Most often, the polarization occurs in a plane perpendicular to the surface.

Substances are described as dextrorotatory or levorotatory according to whether the plane of polarization is rotated clockwise or counterclockwise, respectively, as determined by viewing towards the light source. Dextrorotation is designated (+) and levorotation is designated (-).

1. Linear polarization is when the oscillation of a wave is constrained to a single plane. This is the plane of polarization.

Define polarization of light in physicsclass 12

Such a medium contains lots of atoms and when an unpolarized light beam strikes an atom it transfers energy to an atom. As a result, an electron in that atom starts vibrating in response to the electric component of the incident ray. Now, this vibrating electron emits E.M radiation in all directions, and this forces neighboring electrons to undergo a similar process. This phenomenon of absorption and emission of the electromagnetic radiation is known as the scattering of light.

When we restrict vibration to an electrical vector in an unpolarized light we get plane polarized light. In this the direction of vibration of electric vector and direction of light propagation are perpendicular to each other as shown below.

Polarized and unpolarizedlight

However the scattered light can be unpolarized, partially polarized, or completely polarized based on the direction of the incident ray as shown below.

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2. Circular polarization is when two linear components of a wave oscillate perpendicular to each other such that their amplitudes are equal.

3. Elliptical polarization is the same as circular polarization except that the amplitudes and phase differences are not the same.

There are three main types of polarization namely, linear polarization, circular polarization, and elliptical polarization.

The velocity and refractive index of extraordinary waves changes with direction whereas for ordinary ray velocity remains constant throughout the crystal while propagating.

The two rays of light are each plane-polarized by the calcite such that the planes of its polarization are mutually perpendicular to each other as shown below.

Polarization due to scattering can be seen through the sky as we can see below. When an unpolarized beam of sunlight passes through the atmosphere the light scatters down towards earth. Also it has no vertical polarization.

For this experiment let’s consider that we have an unpolarized light passing through two polarizer T1 and T2, here line on polarizer shows plane of vibration i.e., the plane in which electric field vector can vibrate freely, whereas electric field perpendicular to this line will be eliminated completely.

Q: A sugar solution in a tube of length 2.0 dm produces optical rotation of 12°. Then, the sugar solution to one half of its initial concentration. If the dilute solute solution is contained in another tube of length 3.0 dm, the optical rotation produced by it will be

Light passing through a calcite crystal is split into two rays as shown below. This process is called double refraction or polarization by refraction.

So, as we discussed above, light is a transverse wave, and confining the plane of vibration of such a transverse wave by the principle of scattering is termed Polarization by scattering.

And hence from this experiment we can conclude that electric fields are vibrating perpendicular to its direction of propagation, hence light is a transverse wave.

Double refraction, also known as birefringence, is an optical property in which a single ray of unpolarized light entering an anisotropic medium is split into two rays i.e., ordinary & extraordinary rays, each traveling in a different direction.The concept of Double refraction can be observed by comparing two materials, glass and calcite.