Measuring with Light Waves

Interferometers from the workshop to LIGO

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

• An interferometer turns path differences into brightness changes.
• Moving a mirror by λ/2 shifts one fringe, so tiny movements can be measured.
• LIGO combines high power, many bounces and squeezed light to sense 10⁻¹⁸ m.

Steps

1. Michelson’s interferometer
2. Counting fringes
3. A millimetre of fringes
4. LIGO again
5. Reading the fringes
6. Squeezed light