6 TTW Bernardustechnicum Oudenaarde
Polarization by reflection
Polarization by reflection
Goal
To prove that light is polarized by reflection
Materials
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Laser + battery
A transparent cube
Paper
A set square with integrated protractor
A polarization filter
Method
Setup to define refractive index
We place the transparent cube on a white sheet of paper. We focus the laser light on the cube under
a known angle of incidence. Draw and calculate the angle of incidence and the angle of refraction.
(make sure that the angle of incidence is big enough to draw)
Calculate the index of refraction with the formula.
Make sure that your calculator is in the degrees modus!
Setup of light that falls under the Brewster angle
We calculate the Brewster angle , needed for our setup, with the formula Ө=tan-1(n).
Equalize the angle of incidence of the light to the calculated Brewster angle. If the setup is drawn up
correctly, you can look through the polarization filter to see whether the reflected light is polarized.
You do this by turning the filter, if you see the reflected light wane by turning the filter you know it’s
polarized.
When natural light/daylight is focused on a transparent surface, the preferred direction of reflected
light will be perpendicular to the angle of incidence. Vibrations in reflected light mainly run
horizontally. That is why polarizing filters are used in photography to counter disturbing reflections.
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6 TTW Bernardustechnicum Oudenaarde
Polarization by reflection
Polarization by reflection only occurs when light shines on a transparent surface. Part of the light
penetrates the surface, refraction takes place and a partial polarization occurs. The other part of the
light is reflected and polarized in the other direction.
Setup refractive angle
Setup Brewster angle
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