An optical spectrometer or simply spectrometer is an apparatus to record the intensity distribution as a function of the wavelength of a light source. Spectrometer played and still play an important role in a variety of applications.  The emitted radiation from a source provides information about the atomic and molecular energetically structure. It is a keyhole to the fascinating world of quantum mechanical and optical processes. The first spectrometer used prisms to achieve the required spatial separation of the incoming light. By using a precise goniometer the exit angle is measured and set into relation of the wavelength. The emerging optical gratings made the spectrometer more precise and enhanced the resolution significantly. Another step towards more convenient use can be seen in the development of two dimensional CCD chips allowing the real time measurement and data storage with computer. Last but not least the optical fibre made it very comfortable to bring the light to the spectrometer. Today’s spectrometer are available in a size of halve a brick providing a spectral range from 200 to 1200 nm with a resolution of 1 nm. Such a spectrometer is part of this experiment to train the students in the application of the most import optical measuring apparatus. Within the scope of the experiments three different light sources are used and characterised by the spectrometer. The spectra of a white light, a NIR LED and a incandescent lamp are compared and discussed. Two optical filter are placed in the front of the light sources and the transmission spectrum recorded.