Returns the index at which the wavelength given in nm can be found in a vector (i = 1: 200nm, i = 2: 202.5nm, ..., i = 217: 740nm).
Returns the index at which the wavelength given in nm can be found in a vector (i = 1: 200nm, i = 2: 202.5nm, ..., i = 217: 740nm).