Summarizing Polarization

Polarization Summary

• Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave.
• EM waves are transverse waves that may be polarized.
• The direction of polarization is defined to be the direction parallel to the electric field of the EM wave.
• Unpolarized light is composed of many rays having random polarization directions.
• Light can be polarized by passing it through a polarizing filter or other polarizing material. The intensity \(I\) of polarized light after passing through a polarizing filter is \(I={I}_{0}\phantom{\rule{0.25em}{0ex}}{\text{cos}}^{2}\phantom{\rule{0.25em}{0ex}}\mathrm{\theta ,}\) where \({I}_{0}\) is the original intensity and \(\theta \) is the angle between the direction of polarization and the axis of the filter.
• Polarization is also produced by reflection.
• Brewster’s law states that reflected light will be completely polarized at the angle of reflection \({\theta }_{\text{b}}\), known as Brewster’s angle, given by a statement known as Brewster’s law: \(\text{tan}\phantom{\rule{0.25em}{0ex}}{\theta }_{\text{b}}=\cfrac{{n}_{2}}{{n}_{1}}\), where \({n}_{1}\) is the medium in which the incident and reflected light travel and \({n}_{2}\) is the index of refraction of the medium that forms the interface that reflects the light.
• Polarization can also be produced by scattering.
• There are a number of types of optically active substances that rotate the direction of polarization of light passing through them.

Glossary

axis of a polarizing filter

the direction along which the filter passes the electric field of an EM wave

birefringent

crystals that split an unpolarized beam of light into two beams

Brewster’s angle

\({\theta }_{\text{b}}={\text{tan}}^{-1}\left(\cfrac{{n}_{2}}{{n}_{1}}\right),\) where \({n}_{2}\) is the index of refraction of the medium from which the light is reflected and \({n}_{1}\) is the index of refraction of the medium in which the reflected light travels

Brewster’s law

\(\text{tan}\phantom{\rule{0.25em}{0ex}}{\theta }_{\text{b}}=\cfrac{{n}_{2}}{{n}_{1}}\), where \({n}_{1}\) is the medium in which the incident and reflected light travel and \({n}_{2}\) is the index of refraction of the medium that forms the interface that reflects the light

direction of polarization

the direction parallel to the electric field for EM waves

horizontally polarized

the oscillations are in a horizontal plane

optically active

substances that rotate the plane of polarization of light passing through them

polarization

the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave

polarized

waves having the electric and magnetic field oscillations in a definite direction

reflected light that is completely polarized

light reflected at the angle of reflection \({\theta }_{\text{b}}\), known as Brewster’s angle

unpolarized

waves that are randomly polarized

vertically polarized

the oscillations are in a vertical plane