The Open Door Web Site
WAVES
 Custom Search
Polarization: Malus' Law
 Polarized light has several practical uses. Polarized light can be obtained by sending unpolarized (randomly polarized) light through a polarizing filter for example "Polaroid". Polarization can also be produced by reflection from the surface of a transparent medium (water, glass etc). In most situations using polarized light we actually use two identical filters. The first filter is called the polarizer (for obvious reasons!) and the second, which can often be rotated relative to the first, is the analyzer. In the following diagrams, the red arrows indicate the orientation of the plane of polarization of the filters. After passing through the first filter, the light has electric field only in one plane (in this case, vertical). This polarized light is therefore allowed to pass by the second filter as it is placed with its plane of polarization parallel to the first. Now, with the analyzer perpendicular to polarizer, no transmitted light With polarizer and analyzer at some other angle, θ, the amplitude of the transmitted light waves is equal to component of the amplitude of the polarized light parallel to the plane of the analyzer. Therefore the amplitude of the electric field vector of the transmitted light is Ecosθ as shown here. The intensity of a wave is a measure of the energy it transfers per unit time per unit area (Wm-2) The intensity of a wave is proportional to the square of its amplitude. So, in this case, we can say that the intensity, I of the transmitted light will be given by where Io is the intensity of the light incident on the polarizing filter (the analyzer in the case above). This statement is referred to as Malus' law after the French physicist Etienne-Louis Malus.
 © The Open Door Team2016Any questions orproblems regardingthis site should beaddressed tothe webmaster © David Hoult 2017 Hosted By

Waves Index Page