Light and Color

Coated Optics

By coating a piece of glass with an extremely thin clear coating (1/2-wavelength thick), one can keep light from reflecting from the surface. The thickness of the coating is designed so that the reflections from the front and rear surfaces destructively interfere, cancelling the reflection. The disks in this exhibit only have a central spot coated so that the difference can be observed. The anti-reflection coating also makes the glass more transparent (less loss).