Physics Study Guide/Quantum Mechanics

The Beginning Of The End

By the start of the twentieth century, a major problem had become apparent in what is now referred to as 'classical physics'. The Rayleigh-Jeans Law of thermodynamics stated that as the wavelength of the light incident on a hot body, the total power reflected from the body would also increase. The problem with this was that as the wavelength increased towards zero, the power increased towards infinity. This peak occurred about the ultraviolet section on the EM spectrum so the problem became known as the Ultraviolet Catrastope. This marked the beginning of the end for classical physics.

However, in 1900, a physicist named Max Planck went before the German Physical Society and presented a groundbreaking new theory on thermal radiation. It was based on an idealised body called a blackbody - perfect absorber and emitter of radiation. The emission spectrum of this body is identical to that of classical theory until it reaches a specific wavelength, dependent on the temperature of the body, where it peaks and then drops to zero for the shortest wavelengths.