Twisting Light

Optical activity

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Enantiomers rotate polarised light by equal and opposite angles.
• Racemic mixtures don’t rotate light; e.e. = observed ÷ pure rotation.
• R/S and +/− are independent.

Steps

1. A polarimeter
2. Light with a twist
3. Measure a rotation
4. A 50:50 mix
5. Enantiomeric excess
6. R is not +