Polarization
An ordinary light beam consists of many waves emitted by the atoms of a light source. Each atom produces a wave having some particular orientation of the electric field vector. The magnetic field B associated with the wave is perpendicular to the field E, and both are perpendicular to the direction of propagation.
The direction of polarization of each wave is defined by the direction in which the electric field E is vibration. This direction lies along the y-axis. However, an electromagnetic wave could have its, E vector in the OZ plane making an angle with y-axis. Because all directions of vibration from a wave source are possible, the resultant electromagnetic wave is a superposition of a wave vibrating in many directions. This gives a polarized light beam, which propagating in a direction perpendicular to the plane of the paper. The arrows show a few possible directions of vibration of the electric field vectors for the individual waves making up the resultant wave.
A wave is said to be linearly polarized if the resultant electric field E vibrates in the same direction at all time at a particular point, as shown. The wave is then called the linearly or plane polarized. The plane formed by E and the direction of propagation is called the plane of polarization of the wave. If the wave represents the resultant of all individual waves, the plane of polarization is the XY plane.
Plane of vibration
The plane formed by E vector and the direction of propagation is called the plane of vibration.
Plane of polarization
A plane at right angle to the plane of vibration is called the plane of polarization.
Polaroid
A Polaroid is a device used to produce a plane polarized light. It consists of a long chain of molecules aligned in a particular direction. Such device is made from crystals of dodo sup hide or quinine in thin sheet mounted between two thin sheets of glass or cellulose. These crystals are also called Hera pat hide.
Polaroid
A Polaroid is a device used to produce a plane polarized light. It consists of a long chain of molecules aligned in a particular direction. Such device is made from crystals of dodo sup hide or quinine in thin sheet mounted between two thin sheets of glass or cellulose. These crystals are also called Hera pat hide.
When a polarized light falls on a Polaroid, the electric vector E oscillating in the direction of the alignment of molecules of the Polaroid is observed. However, electric field vector oscillating in the direction perpendicular to the alignment of molecules pass through the Polaroid. So, the transmitted light has an electric field vector oscillating perpendicular to the direction of the alignment of the molecules of the Polaroid. Transmitted light is known as linearly or plane polarized light, and the direction perpendicular to the alignment, of the molecules of the Polaroid is known as transmission axis or polarizing direction. The vertical lines shown on the surface of the Polaroid are polarizing directions. When two Polaroids are parallel to each other, the polarizing direction are parallel to each other and the light transmitted by the first Polaroid is also transmitted by the second Polaroid.
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