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Page 1

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Polarisation
Transverse waves only.
Unpolarised waves ­
plane of wave
oscillation is randomly
orientated.

Page 2

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Polarisation
Plane polarised waves ­
all waves have
matching planes of
oscillation e.g. vertical
or horizontal.

Page 3

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Polarisation
In this example, the
polariser's "preferred
plane of polarisation" is
vertical.




This means it will only
let through vertically
polarised waves and
absorb the rest.

Page 4

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Polarisation
A polariser for
microwaves is made
from parallel metal
bars.




A polariser for optical
wavelengths is made
from parallel polymer
chains.

Page 5

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Polarisation
Charged particles are
free to oscillate along
the metal bars (or
polymer chains)




So they absorb
electromagnetic waves
which oscillate parallel
to those bars/chains

Page 6

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Aerials
Examples of polarised
(selective) absorbers ­
Short horizontal metal
bars on television
aerials. (Therefore TV
broadcasts are
horizontally plane
polarised)

Page 7

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Sunglasses
Polymer chains in
certain plastics ­
Polaroid sunglasses.
Reflected glare from
horizontal surfaces is
horizontally plane
polarised. Horizontal
polymer chains in
polarising sunglasses
only let through
vertically polarised light
(and so block the glare)

Page 8

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Malus's Law
If the angle of rotation
between two parallel
polarisers is then the
Intensity, I of the
transmitted light is
given by:

I =Io Cos2

Where Io is the incident
intensity on the second
polariser.

Page 9

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Malus's Law

I =Io Cos2

Page 10

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Three Videos

VIDEO
... for polarisation with
light and microwaves.

VIDEO
... for 3D Cinema
Polarisers.

VIDEO
...for Circular
Polarisation.

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