Why are fringes are formed in the Young double slit experiment?

In the Young double slit experiment, coherent light of wavelength λ from a single source illuminates a system of two slits separated from each other by a small distance a. Each slit causes the light entering it to diffract, and behaves like a light source. Light from each slit is then observed on a screen at a distance D far away from the set of slits.At certain points on the screen, the light waves from each slit arrive in phase (phase difference of 2nπ, with n an integer) with each other, due to the difference in the length the waves have travelled (path difference) being nλ. This causes constructive interference and produces a bright fringe. At other points, the waves from each slit arrive in anti-phase (phase difference of (2n+1)π), corresponding to a path length of (2n+1)λ/2, causing destructive interference and producing no resultant wave which looks like a dark fringe. As a result, an alternating pattern of light and dark fringes is formed. The spacing Δx between light fringes is found using Δx = Dλ/a.

JP
Answered by Joe P. Physics tutor

9836 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

What is an equipotential in an electric/gravitational field?


Explain how a stationary wave is produced when a string fixed at both ends is plucked


If a 10N tension force is exerted on a steel beam (E = 200 GPa) with cross-sectional area 1cm^2, what is the stress acting on the beam? What is the change in length of the beam, if the beam is 10cm long?


What is wave-particle duality?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences