What is fringe in wave optics?

Fringe in Wave Optics

In wave optics, a fringe is a bright or dark band on a screen produced by the interference or diffraction of light waves.

Types of Fringes

• Bright fringe: forms where waves arrive in the same phase (constructive interference).
• Dark fringe: forms where waves arrive out of phase (destructive interference).

Example: Young’s Double Slit Experiment (YDSE)

Monochromatic light passing through two narrow slits produces overlapping wavefronts on a distant screen. The superposition creates an alternating pattern of bright and dark fringes—an interference pattern characteristic of coherent light sources.

Fringe Width (YDSE)

Δx = (λ · D) / d

where Δx is fringe width, λ is the wavelength of light, D is the distance from slits to screen, and d is the separation between the slits.