# A Question About Brewster's Law

In most textbooks I read, they state that when the angle of reflection + angle of refraction = 90, there is maximum polarization. What I don't understand is what maximum polarization means. Does it mean that the polarized light is of the highest intensity? Does it mean that most of the light beam is polarized when reflected at that angle, as compared to any other angle? What does it mean? Please explain this at the level of a high school student.

• How do i cancel the downvote ? – Abhirup Mukherjee Oct 23 '18 at 17:12
• @AbhirupMukherjee: after a 5-minute grace period, downvotes are "locked in" unless and until the question is edited. If someone edits the question, then you'll be able to remove the downvote. – Michael Seifert Oct 24 '18 at 13:56

We can quantify how much a beam is polarized by looking at how much the intensity of the polarizations differs, expressed as a fraction of the total intensity: $$\text{polarization} = \frac{|I_A - I_B|}{I_A + I_B} \times 100\%,$$ where $$I_A$$ and $$I_B$$ are the intensities of the the two possible polarizations. If, for example, all of the light intensity in the original beam is in polarization $$A$$, and none is in $$B$$, then you'll get a polarization of 100%. On the other hand, if the intensities of the two polarizations are equal, you'll get 0% polarization, i.e. the original beam was unpolarized. If one of the polarizations is brighter than the other, but both polarizations have some intensity, then you'll get somewhere in between, i.e., partial polarization.