You searched for: “angstrom unit”
angstrom unit, symbol: A or Å
A length equal to 10-10 meters or one-ten-millionth of a millimeter, used for atomic measurements and the wavelengths of electromagnetic radiation.
A unit that measures the wavelength of light and equals 0.00000001 of a centimeter. Blue light has a wavelength of about 4400 angstroms, yellow light 5500 angstroms, and red light 6500 angstroms.