how to measure light wavelength exactly?

silin

Hi people,

does anybody know what the simplest device that can be used to measure monochromatic light wavelength exactly? Thanks.

OlderDan

The simplest ways I can think of involve interference. For example, you can use:
A diffraction grating (probably the best)
A pair of optical flats with high precision spacers
An optical flat and a precision plano convex lens of known radius to form Newton's rings.