Diffraction
The bending, spreading, and interference of light waves around the edges of an obstacle or through a narrow aperture.
Governing formula
a sin θ = m λ (Single Slit Minima)
SI unit
m
In depth
Diffraction is a fundamental wave phenomenon occurring when aperture size a is comparable to light wavelength λ. It limits the ultimate resolution of optical instruments according to the Rayleigh criterion.
Examples in the real world
Laser light passing through a pinhole forming concentric bright and dark Airy rings on a distant screen.