Diffraction of light (i.e. the deviation of the linear propagation) and interference (i.e. the coherent superposition of light waves results in intensity maxima and minima) represent central phenomena of wave optics. Moreover, both phenomena are playing an essential role in techniques (e.g. resolution of optical instruments) and in nature (e.g. the colour impressions of wings of butterflies or of a CD-ROM). In this experiment laser light is shining on objects (such as single slit, double or multiple slits, and gratings) which can be chosen by the remote user. Light waves are diffracted by such an object and the elementary waves superimpose on a screen. The intensity pattern can be qualitatively observed on that screen or quantitatively analyzed.