Jones calculus is a matrix method for following polarized light through filters, retarders and crystals. R.C. Jones published it in 1941.
In more detail
Each element is a 2 × 2 matrix acting on the light's vibration. Between crossed polarizers, a plain retarder passes I = sin²2φ sin²(γ/2) of the light. Here φ is the turn of the retarder and γ is its retardance.
How we measure it
The Polariscope computes everything by Jones calculus at 81 wavelengths. It uses the refractive indices and measured absorption of each stone.
Related terms
- 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.
- Polarized light: 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.
- Birefringence: Birefringence is the difference between the two refractive indices of a doubly refractive stone. It shows how strongly the stone splits light into two rays.