Brewster's Angle Calculator

At the Brewster angle the reflected light is completely polarized parallel to the surface, which is why polarized sunglasses cut glare so effectively.

For light passing from air into glass with a refractive index near 1.5, the Brewster angle is about 56 degrees from the normal.

For light passing from air (index 1.00) into water (index about 1.33), the Brewster angle is arctan(1.33), which is roughly 53 degrees from the normal. This is why polarized sunglasses are so effective at cutting glare reflected off lakes and wet roads.

At the Brewster angle the reflected and refracted rays are exactly 90 degrees apart, so θ_B + θ_refracted = 90°. The reflected light is radiated by the oscillating charges in the second medium, and those charges cannot radiate along their own axis of oscillation. When the refracted ray points that oscillation straight toward the reflected direction, the parallel-polarized reflection vanishes and only fully polarized light remains. Combining this geometry with Snell's law yields the simple result tan θ_B = n₂ ÷ n₁.