It is a well known fact that hot bodies emitting optical radiation from ultraviolet to infrared. The spectrum shows a peak, which depends on the temperature of the body. This phenomenon attracted the scientist Rayleigh and Jeans to find an theoretical model for this. However, all their attempts failed and the correctly formulated solution predicted infinite power in the UV range of the spectral emission. It was Max Planck finding a way out or the so called UV catastrophe by defining a new constant h and accidentally initiated a new physics, the quantum mechanics.

In our experiment we will track some steps which lead at the beginning of the 20th century to a new understanding of the interaction with light and matter. We will use a kind of black body radiator in form of a incandescent tungsten lamp. The emitted light is captured by a spectrum analyser in real time. With a precise current and voltage applied to the tungsten filament the temperature of it is determined. For a series of temperature values the emitted spectrum is recorded and stored for further analysis. The results are compared with Planck’s law as well as the Wien’s approximation. Since the spectrometer is fibre coupled and very compact the spectrum of the sun can be recorded and based on the results of the previous measurements with the tungsten lamp the temperature of the sun is determined.