Miscellaneous detailing related content
A spectrometer is a device that is capable of measuring certain characteristics of light. This is most often displayed as light-intensity, but can also refer to polarization and refractive qualities. A spectrometer can be used to determine the color of paint, very expensive models can even be capable of determining the material used.
The refractive index is a way of measuring how lights behaves through a certain medium. This number gives an indication of how light reacts and how light is reflected. Manufacturers use (among other things) this as an indication of how light is reflected by a protective product and how that will make the surface look.