In Michelson'* interferometer the yellow sodium line composed of two wavelengths λ1 = 589.0 nm and λ2 = 589.6 nm was used. In the process of translational displacement of one of the mirrors the interference pattern vanished periodically (why?). Find the displacement of the mirror between two successive appearances of the sharpest pattern.
Interference pattern vanishes when the maxima due to one wavelength mingle with the minima due to the other. Thus
where Δh = displacement of the mirror between the sharpest patterns of rings
