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
Subhamiltonian graph therefore also subhamiltonian; these include the 4-connected planar graphs and the Halin graphs. Every planar graph with maximum degree at most four is subhamiltonian, as is every planar graph with no separating triangles. If the edges of an arbitrary planar graph are subdivided into paths of length two, the resulting subdivided graph is always subhamiltonian. Subhamiltonian graph In graph theory and graph drawing, a subhamiltonian graph is a subgraph of a planar Hamiltonian graph. A graph "G" is subhamiltonian if "G" is a subgraph of another graph aug("G") on the same vertex set, such that aug("G") is planar and contains