Reciprocal length or inverse length is a measurement used in several branches of science and mathematics. As the reciprocal of length, common units used for this measurement include the reciprocal metre or inverse metre (m−1), the reciprocal centimetre or inverse centimetre (cm−1), and, in optics, the dioptre.
Quantities measured in reciprocal length include:
- absorption coefficient or attenuation coefficient, in materials science
- curvature of a line, in mathematics
- gain, in laser physics
- magnitude of vectors in reciprocal space, in crystallography
- more generally any spatial frequency e.g. in cycles per unit length
- optical power of a lens, in optics
- rotational constant of a rigid rotor, in quantum mechanics
- wavenumber, or magnitude of a wavevector, in spectroscopy
- density of a linear feature in hydrology and other fields; see kilometre per square kilometre
- Barrett, A. J. (11 July 1983). "A two-parameter perturbation series for the reciprocal length of polymer chains and subchains". Journal of Physics A: Mathematical and General 16 (10).