The centimeter (abbreviation, cm) is a unit of displacement or length in the cgs (centimeter/gram/second) system of units. One centimeter is the distance traveled by a ray of electromagnetic (EM) energy through a vacuum in 3.33564095 x 10-11 of a second. It is equivalent to 0.01 meter. There are about 2.54 centimeters in one linear inch.
Power-of-10 prefix multipliers facilitate the derivation of other, often more convenient, distance units from the centimeter. One meter (m) is equal to 100 cm, one millimeter (mm) is equal to 0.1 cm, and one kilometer (km) is equal to 100,000 (105) cm. These units are found in nonscientific as well as scientific literature. Smaller units are the realm of the scientist and engineer. One micrometer (symbolized µm or µ), also called a micron, is equal to 0.0001 (10-4) cm. One nanometer (nm) is equal to 10-7 cm. One Angström unit (symbolized Ä) is equal to 10-8 cm, or 0.1 nm.
The centimeter and its kin are used to specify the wavelengths of EM fields, particularly at ultra-high and microwave radio frequencies. The so-called radio spectrum occupies an informally defined range of wavelengths from roughly 1 mm to several tens of kilometers. A 300-cm radio wave falls near the middle of the standard FM (frequency-modulation) broadcast band; a 1-cm radio wave corresponds to a frequency of approximately 30 gigahertz (GHz). The range of visible light wavelengths is from approximately 390 nm (violet) to 770 nm (red). The speed of EM-field propagation in a vacuum, to nine significant figures, is 2.99792458 x 1010 centimeters per second.