The Open Door Web Site
HOME PAGE BIOLOGY CHEMISTRY PHYSICS ELECTRONICS HISTORY HISTORY of SCI & TECH MATH STUDIES LEARN FRENCH STUDY GUIDE PHOTO GALLERY
ATOMIC and NUCLEAR ELECTRICITY and MAGNETISM MEASUREMENTS MECHANICS OPTICS PRACTICAL WORK QUESTIONS RELATIVITY THERMAL PHYSICS WAVES
WAVES
Google
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.  
SITE MAP
WHAT'S NEW
ABOUT
PRIVACY
COPYRIGHT
SPONSORSHIP
DONATIONS
ADVERTISING
 

© The Open Door Team
2016
Any questions or
problems regarding
this site should be
addressed to
the webmaster

David Hoult 2017

Hosted By
Web Hosting by HostCentric

 
SiteLock
 
 
Waves Index Page