Physics: Light & Optics

[basketballakev]

Ehh can someone please explain to me how to solve this problem? Thanks a lot!

When unpolarized light reflects off of a specular (mirrored) surface at a glancing angle with respect to the surface, light can partially polarize parallel to the surface. That is, the parallel polarized light is more intense than the perpendicular polarized light. If this surface is lying on flat ground, in what orientation should a polarizing anti-glare filter be with respect to the ground, in order to minimize the toal light intensity through the filter? The polarizer's polarization axis should be oriented at:

A. 0 degrees with respect to the ground.
B. 45 degrees with respect to the ground.
C. 90 degrees with respect to the ground.
D. 180 degrees with respect to the ground.

The anser is C.

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[Phlame217]

This requires no knowlege of physics to solve, as the answer lies in the question along with the explanation.

Basically it says the smaller the incedence angle of the unpolarlized light, the more energy the light is going to have when its reflected. Therefore the most energetic light is going to be the light that doesn't hit the mirror at all, but runs parallel to it.

The questions wants to use a filter to reduce te polarized light to the least amount of energy, therefore the most energetic light, running parallel, must be directly filtered.

This leads one to realize that the filter must be placed perpendicular to this light, which happens to be perpendicular to the ground as well, aka 90 degrees (C).

Another way to solve it quickly is to quickly eliminate A and D cuz their the same answer pretty much, and always thing of a force in general which says a force is at its maximum when it is acting at right angle to the object (aka torque and all). the words parallel should then trigger thoughts of being perpendicular aka 90.