Polarization
Polarized light oscillates in a single plane.
About this topic
Polarisation restricts the oscillations of a transverse wave to a single plane. Unpolarised light vibrates in all directions; a polarising filter passes only one direction. Two filters at 90° block light entirely, and in between intensity follows Malus's law, I = I₀cos²θ.
Glare reflected off water or roads is partly polarised horizontally, so polarising sunglasses with vertical transmission axes reduce it. LCD screens in phones and calculators use polarisers with liquid crystals that rotate the light's plane to switch pixels on and off. Polarisation shows that light is a transverse wave, since longitudinal sound waves cannot be polarised.
Worked example: unpolarised light passing through the first filter loses half its intensity. If a second filter is rotated 60 degrees to the first, the intensity is multiplied by cos²60 = 0.25. So starting with 100 units, 50 pass the first and 12.5 pass the second. Putting a third filter at 45 degrees between two crossed ones surprisingly lets some light through.
Applications include photography filters, 3D cinema glasses, stress analysis in plastics and astronomy. A misconception is that a polariser works like a grid of slits to let one direction through; it is more subtle, but this picture works for understanding. Another is that sound can be polarised in air, which it cannot.
Key ideas
- Only transverse waves polarize
- Sunglasses cut glare
- Used in LCD screens
Quick check
Use cases: where Polarization helps
- Homework: review the key idea behind Polarization before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Polarization without notes.
- Visual learning: play with the interactive lab to see how Polarization changes when you adjust its inputs.
- Teaching a friend: explain Polarization in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Polarization?
Polarized light oscillates in a single plane.
What will I learn in Polarization?
Only transverse waves polarize. Sunglasses cut glare. Used in LCD screens.
Is Polarization part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Polarization lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Polarization?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.