Question

To find the wavelengty of monichromatic light using etalon

Answer 1

Monochromatic light falling on the etalon mirrors travel back and forth between the two mirrors. If this back and forth distance traveled between the mirrors equal an integral number of wavelength (λ, 2 λ 3 λ …nλ) then maximum light escapes through the mirror M2 and constructive interference occurs forming bright ring.