Polarisation

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A physicist is just an atom's way of looking at itself.
Read more at http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99

A physicist is just an atom's way of looking at itself.
Read more at http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99

A physicist is just an atom's way of looking at itself.
Read more at http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99

A physicist is just an atom's way of looking at itself"
Niels Bohr

We have seen that electromagnetic waves may be described by transverse waves of E and B (at right angles to each other). However, there is nothing special about any particular direction for the E or B vectors to oscillate. In fact an unpolarised wave contains waves with E vectors in all possible directions (for each E wave there is a B wave at right angles). If the wave propagates in the z direction this wave has E components in all possible directions.

In a polarised wave the E vector oscillates in a specific direction - the direction of polarisation.

Polarised light does not appear any different to unpolarised light to our eyes. The difference only becomes apparent when observing through transparent polarising material,

polarisation fig1

polarisation fig2

The intensity of initially unpolarised light which passes through two polarisers is given by Malus' Law,

where I₀ is the incident intensity and θ is the angle between the directions of the two polarisers. Note that for "cross polarisers" there is no transmitted wave.

Analog TV and radio signals are transmitted as polarised waves. When rotating the direction of an antenna you are effectively rotating the second polariser, thus varying the angle θ. Maximum and minimum signal reception will be obtained with orientations of the antenna at ninety degrees to each other.

"Alimony is like buying hay for a dead horse"
Groucho Marx

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu