The Blackbody Experiment

The blackbody radiation experiment is performed by using a tungsten filament. Different voltages mean different temperatures for the filament.

From Wien to Planck’s Law ( Origin of E=h𝛎)

Textbooks usually do not mention how exactly the “quantum of energy” was introduced by Planck. What Planck did is what we today call a pro-gamer move. There was this data from blackbody radiation experiments that had to fit a scientific explanation. While Wien’s explanation and formula (for obtaining intensity at a given wavelength/frequency) explained the high frequency data accurately, it did not work for lower frequencies (see fig. below). However, Wien’s curve fit the data pretty closely. So Planck put Boltzmann’s work (not Rayleigh Jeans’ work, as popularly believed) into Wien’s work and for that formula to work, E had to be equal to hv. And that kids, is how E became equal to h𝛎.

Source and detailed explanation



Max Planck made this equation in 1900, and until then it was just an idea. But in 1905, Albert Einstein proved E=h𝛎 using the photoelectric effect. A mystery until then, the photoelectric effect had puzzled many scientists. Albert Einstein explained that the effect was nothing but the manifestation of quantized energy. Kinetic energy of the ejected photo-electrons was known to be proportional to the frequency of the light radiated on the metal. Einstein put Planck’s hypothesis into the picture, and out came the same value of h that plack had obtained putting his equation into the blackbody radiation data. E=h𝛎 was confirmed. This marked the beginning of quantum mechanics.