Direct reflected light that has been polarized is similar to un-polarized reflection in that it reflects off a surface at the same angle as it strikes so that to view the reflection you have to be in line with the angle of reflection or in other words within the family of angels. However, polarized light reflects less brightly than direct reflection, pure reflected un-polarized light if half as intense as the original light source. Normally un-polarized light is more than half as a result of some light absorbing qualities found in many materials.
What is polarized light?
Returning to what light is, light is a photon with the electromagnetic field fluctuating around it.
Un-polarized light
This electromagnetic field can be visualized with two children holding a skipping rope, the rope representing the electromagnetic field fluctuating from positive through zero to negative through zero to positive. One child swing her end of the rope whilst the other child holds her end still, this produces a visual picture.
Polarized light.
To polarize the light, imagine that the children are now standing on either side of a picket fence with the rope between them as the child swing the rope on one side of the fence, the child on the other side who holds the rope still, finds her end of the rope in bouncing up and down instead of swinging. We now have a visual image of polarized light.
Blocking polarized light.
Now to see a visual representation of a filter at work blocking polarized light, we simply add horizontal bars across the picket fence and threat the rope though a gap between two vertical pickets and two horizontal bars. One child again swings the rope from her side of the fence whilst the other child simply hold the rope still.
The child simply the rope now sees that her side of the rope doesn’t move at all.
This is blocked polarized light and is therefore invisible to the eye or camera.
A large body of water such as a lake, painted metal, glossy wood and plastic are typical sources of direct reflected polarized light.
Polarized direct reflection is most easily seen in black or transparent objects as they do not produce strong reflected light but weaker diffused light instead.
Taken from the book:
Light, Science & Magic, 4th edition. By Fil Hunter, Steven Biver, Paul Fuqua.
Published by Focal Press, Taylor & Francis Group.