Brewster's Law and Polarization by Reflection
For incidence from medium n1 into n2, Brewster angle i_B satisfies tan(i_B)=n2/n1. At this angle i_B+r=90 degrees, and the reflected light is polarized perpendicular to the plane of incidence.
Why this shows up in the exam
Polarizing sunglasses · Reducing reflection in imaging · Measuring refractive index
Learn the idea
At Brewster incidence, reflected light is linearly polarized and reflected and refracted rays are perpendicular. At one special tilt, the reflected electric-field component in the plane of incidence vanishes, leaving only the perpendicular component.
🧠 Memory hook: Brewster makes reflected and refracted rays a right angle.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- tan(i_B) = n2/n1 — Brewster's law
- i_B + r = 90 degrees — perpendicular reflected and refracted rays
- n1 sin(i_B) = n2 sin(r) — Snell's law at the interface
How to approach it
- 1Identify incident and transmitted media
- 2Use tan(i_B)=n2/n1
- 3Use i_B+r=90 degrees for direction questions
Common slip-ups that cost marks
- •Using n1/n2 instead of n2/n1
- •Saying reflected polarization lies in the incidence plane
- •Using the critical-angle relation at Brewster incidence
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A real object is placed 30 cm from a converging lens of focal length 10 cm. Find the real image distance.
More from Optics
Interference of light
Examine the principle of superposition, Young's double slit experiment, fringe width, intensity distribution, and the conditions for constructive and destructive interference.
Diffraction of light
Understand the bending of light around obstacles, single slit diffraction patterns, their width, and the effect of wavelength on diffraction.
Lenses and mirrors
Explore the image formation, ray diagrams, lens and mirror formulas, and the behavior of light with concave/convex lenses and mirrors, including combinations and virtual objects.
Optical instruments
Understand the working principles, magnification, resolving power, and design of devices like microscopes and telescopes, including their adjustments and measurement techniques.
Polarization of light
Learn about the polarization of light, Brewster's law, Malus' law, and the use and function of polaroids.
Dispersion and rainbow formation
Study how light splits into its constituent colors through dispersion in prisms and natural phenomena like rainbows, including minimum deviation and dispersive power.