Question

film of refractive index 1.50 and

thickness 0.25 mm is introduced in the

path of one of the interfering beams of a

Michelson's interferometer. It causes

600 dark fringes to sweep across the

field of view. Calculate the wavelength

of light used.

Answer 1

For wavelength in this case

$$\lambda = \frac{2d(n-1)}{z}$$

Calculating

$\lambda=\frac{2\cdot0.25\cdot(1.5-1)}{600}=416$ nm