For example, if we are studying the composition of a powder mixture using diffuse reflectance, a suitable light source   is directed at the powder mixture and light is collected, usually with a lens, after it has scattered from the powder surface. Light entering a spectrometer first strikes a device (either a grating or interferometer) that separates light of different wavelengths to be measured.
For instance, when examining the composition of a powder blend using diffuse reflectance, an appropriate light source is pointed at the powder mixture, and light is gathered, typically with a lens, after it has scattered off the powder surface. Light entering a spectrometer initially collides with a device (either a grating or interferometer) that distinguishes light of varying wavelengths to be measured.