1) A phenomenon that occurs whenever a light wave is obstructed in any way. Often diffraction fringes can be seen when a small aperture or object blocks light waves. 2) The optical phenomenon by which a grating separates the light into its constituent components. Diffraction causes different wavelengths of light to transmit through or reflect from a grating at different angles, allowing a spectrometer to separate and measure intensity of individual wavelengths.
To learn more about diffraction click on the link to the pamphlet about Solid-State Lighting (LEDs) and on the Laser pamphlet.
1671, from Fr. diffraction, from Mod.L. diffractionem, from L. diffrac-, stem of diffringere "break in pieces," from dis- "apart" + frangere "to break."