Question

In Michelson interferometer when movable mirror is displaced through a distance of 2.5 mm, number of fringes cross the center of the field of view are 50, then the wavelength of the monochromatic light used is

• A. $50\mu m$
• B. $100\mu m$
• C. $25\mu m$
• D. $40\mu m$

Answer 1

The correct option is B $100\mu m$

$\because$ For Michelson interferometer

$n\lambda =2\Delta x$

$\lambda =\frac{2\Delta x}{n}$

$=\frac{2\times 2.5\times {10}^{-3}}{50}=100\mu m$