# Fresnel Loss & Brewster's Angle

1. Apr 10, 2016

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1. The problem statement, all variables and given/known data
I'm trying to understand these two a bit better in terms of lasers.

Fresnel Loss - The loss that occurs when there is a change in refractive index. Some light will be transmitted, while other light will be reflected back into the medium. This is bad for lasers because it could reduce the efficiency of the laser.

Brewster’s Angle -- Is the angle where no light is reflected and all of the light that exits the medium and is polarized.

At Brewster's Angle, is all of the light exiting the medium polarized? or are there now two different polarizations exiting the medium? In the definitions I've seen for Brewster's Angle, they say the reflected light is now polarized and exits the medium, but they don't explicitly mention the 'other' light that originally went through the medium before Brewster's Angle was used to create the polarization.

2. Relevant equations

3. The attempt at a solution

2. Apr 10, 2016

If you have a graph of reflectivity (R) vs. angle of incidence for each of parallel and perpendicular polarization , both go from low values at $\theta=0$ (normal incidence) to R=1.0 at $\theta$=90 degrees. The parallel polarization reflectivity goes down to R=0 at the Brewster angle before going to 1.0 at 90 degrees. The perpendicular polarization reflectivity monotonically increases. In both cases R+T=1.0 without any absorption losses.