. . . . "http://en.wikipedia.org/wiki/Reciprocal_length"^^ . . . "Inverse Length"@en . . . "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."^^ . . . . . . .