Planck's law In 1880, André-Prosper-Paul Crova published a diagram of the three-dimensional appearance of the graph of the strength of thermal radiation as a function of wavelength and temperature. He determined the spectral variable by use of prisms. He analyzed the surface through what he called "isothermal" curves, sections for a single temperature, with a spectral variable on the abscissa and a power variable on the ordinate. He put smooth curves through his experimental data points. They had one peak at a spectral value characteristic for the temperature, and fell either side of it towards the horizontal axis. Such spectral sections are
Graph product lexicographic product serves as a reminder that this product is not commutative. Graph product In mathematics, a graph product is a binary operation on graphs. Specifically, it is an operation that takes two graphs "G" and "G" and produces a graph "H" with the following properties: The terminology and notation for specific graph products in the literature varies quite a lot; even if the following may be considered standard, readers are advised to check what definition a particular author uses for a graph product, especially in older texts. The following table shows the most common graph products, with formula_1 denoting