Ångström
An ångström (symbol: Å) is a unit of length commonly used in physics, chemistry, and biology to measure very small distances, such as atomic and molecular scales. It is equal to 10⁻¹⁰ meters, or 0.1 nanometers (nm).
The unit is named after the Swedish physicist Anders Jonas Ångström, who made significant contributions to spectroscopy.
Key facts:
1 ångström = 10⁻¹⁰ meters = 0.1 nanometers
Used to measure atomic and molecular sizes, wavelengths of light, and crystal lattice constants
Common in fields like crystallography, chemistry, and materials science
Though largely replaced by the nanometer in the SI system, the ångström remains widely used in scientific literature to describe very small lengths.
Femtometer
A femtometer (fm) is a unit of length in the metric system, equal to one-quadrillionth of a meter (1 fm = 10⁻¹⁵ meters). It is also known as a fermi, named after the physicist Enrico Fermi. Femtometers are used to measure extremely small distances at the subatomic level, such as the size of protons, neutrons, and atomic nuclei. For example, the radius of a proton is about 0.84 femtometers. This unit is commonly used in nuclear physics and particle physics, but it's far too small for everyday measurements.
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