The unit used to express wavelengths, such as Ångström and nanometer.
The Ångström unit is named after the physicist Ångström, Anders Jonas. An Ångström unit is equivalent to 0.1 nanometer.
Today, the nanometer is more often used as a unit of length while Ångström is no longer as popular as it used to.
For definition and additional information, see Ångström and nanometer.