---
title: "Polarized light: meaning in gemology"
description: "Polarized light vibrates in one direction across its path, instead of in every direction. A polarizing filter passes only the light that vibrates along its…"
url: https://digitalgemology.com/learn/glossary/polarized-light
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Optics

# Polarized light

Also called polarization

Polarized light vibrates in one direction across its path, instead of in every direction. A polarizing filter passes only the light that vibrates along its own direction.

## In more detail

Two filters at right angles (crossed) pass no light, unless something between them changes the light. Many phone and laptop screens give out polarized light. So never test a polariscope or dichroscope against a screen.

## How we measure it

The Polariscope models ideal polarizers by Jones calculus. Our light-performance tools average Fresnel losses over polarization. Only the simulator's render follows polarization from bounce to bounce, in doubly refractive stones.

## Related terms

- [Polariscope](https://digitalgemology.com/learn/glossary/polariscope): A polariscope is a gem-testing instrument with a stone between two polarizing filters. With the filters crossed, it shows whether a stone is singly refractive, doubly refractive, strained or an aggregate.
- [Doubly refractive](https://digitalgemology.com/learn/glossary/doubly-refractive): A doubly refractive stone splits light into two rays that vibrate at right angles and travel at different speeds. Each ray has its own refractive index.
- [Jones calculus](https://digitalgemology.com/learn/glossary/jones-calculus): Jones calculus is a matrix method for following polarized light through filters, retarders and crystals. R.C. Jones published it in 1941.
- [Fresnel reflection](https://digitalgemology.com/learn/glossary/fresnel-reflection): Fresnel reflection is the share of light that a surface reflects instead of letting through. The Fresnel equations give that share from the two refractive indices, the angle and the polarization.

## Learn more

- [Polariscope](https://digitalgemology.com/about/how-we-measure/polariscope)
- [What we do not model](https://digitalgemology.com/about/how-we-measure/limits)

[All 328 terms](https://digitalgemology.com/learn/glossary)