How this calculator works
For lossless dielectrics, the reflected and refracted rays are perpendicular at Brewster incidence. The reflected beam then contains only the s-polarized component of initially unpolarized light. The simple index ratio assumes non-magnetic transparent media and a single flat boundary. Absorbing materials usually have a reflectance minimum rather than an exact zero.
Formula
tanθB = n2/n1; θt = 90 degrees - θB. Angles are measured from the surface normal.
Worked example
Light entering material of index 1.5 from air of index 1 has a Brewster angle of 56.310 degrees. Equal indices give 45 degrees, although their interface has no reflection at any angle.
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Frequently asked questions
Does all reflected light disappear?
Only the ideal p-polarized component vanishes. The s-polarized component can remain.
Is this the critical angle?
No. The critical angle marks total internal reflection and exists only when entering a lower-index medium.
Can I reverse the media?
Yes. The two Brewster angles are complementary for the same pair of transparent media.