Question

For measuring the wavelength of a manochromatic light source using Michelson interferometer when movable mirror is diplaced through a distance of $4mm$, number of fringes cross the centrer of the field of view are $100$, then the wavelenght of the manochromatic light used is

• A. $40mm$
• B. $80\mu m$
• C. $80mm$
• D. $40\mu m$

Answer 1

The correct option is B $80\mu m$

$\because$ For Michelson interferometer
$n\lambda =2\Delta x$
Where, $n=$ number of fringes corsses
$\lambda =$ wavelength of light
$\Delta x=$ displacement of movable mirror
$\therefore \lambda =\frac{2\Delta x}{n}=\frac{2\times 4\times {10}^{-3}}{100}=80\mu m$