Diffraction Grating
Definition
A surface with thousands of fine parallel lines that splits light into its rainbow spectrum — sharper than a prism.
Unit: m (grating spacing d)
Technical definition
An optical element with periodic slits/grooves (typically hundreds per mm). Constructive interference at angles satisfying d·sinθ = mλ disperses wavelengths precisely. Used in spectrometers to identify elements by their spectral lines.
Example
CD surfaces act as diffraction gratings — the rainbow shimmer is white light split by the disc's microscopic tracks.
Common confusion
A grating separates light by interference, not refraction like a prism — the physics is completely different (path differences vs. dispersion), though both make rainbows.