An "angstrom" (symbol: Å) is a unit of length that is commonly used in the field of nanotechnology, molecular biology, and atomic-scale physics and chemistry. It is named after the Swedish physicist Anders Jonas Ångström, who made significant contributions to the study of spectroscopy and the understanding of atomic and molecular structure.
One angstrom is equal to 0.1 nanometers (nm) or 1 × 10^-10 meters (m). In other words, it is a very small unit of length, often used to describe the size of atoms, molecules, and the wavelengths of electromagnetic radiation such as X-rays and gamma rays.
The angstrom is particularly useful when dealing with structures at the atomic and molecular scale, where measurements are often in the range of a few angstroms. For example, the diameter of a hydrogen atom is about 0.1 angstroms, and the bond length between two carbon atoms in a molecule like benzene is approximately 1.4 angstroms.
A "pole" is a unit of length that is equivalent to 16.5 feet or 5.0292 meters. It is sometimes referred to as a "rod" or a "perch," and these terms are often used interchangeably. Poles, like rods and perches, were historically used in some English-speaking countries, primarily in the United Kingdom and the United States, for land measurement, surveying, and real estate.
While the use of poles, rods, and perches has become less common in modern times, you may still encounter these units of length in certain contexts, especially in older land descriptions or surveys. In everyday measurements and official standards, more commonly used units like meters or feet are preferred.