A good history of the quantum theory, tracing the initial concept up through today’s attempts to unravel this seemingly self contradictory theory. Following are my notes. Kumar does an excellent job of piecing it all together.
Notes:
Plank theorized the quantum in his study of blackbody radiation. Scientists were trying to discover the relationship between peak frequency and temperature. The first theory, Wien’s law, worked for most wavelengths, but broke down in the infrared region. Planck solved the problem by visualizing the blackbody as being made of small oscillators. But, each one could only oscillate at a certain frequency. His formula, E=hv, specifies that v must be a whole number. h is a constant so small, that it’s only relevant on the microscopic level.
Einstein was able to explain why different metals have different threshold points at which they emit light by postulating that frequency is related to specific electron orbits.
Rutherfod ascertained that atoms had a nucleus by firing protons from radiation into different metals–some bounced back at extreme angles.
Bohr’s model was that the electrons were confined to certain orbits.
Balmer created a mathematical formula to explain the relationship between electronic orbit and the spectrum of hydrogen. This led Bohr to realize it was related to electrons jumping between orbits.
Electron orbits were assigned quantum numbers, but they weren’t able to explain all the characteristics–Uhlenbeck proposed adding spin.
In the effort to create a microscope that could see electrons, Heisenberg realized that quantum mechanics predicted that you can’t precisely measure both momentum and position.
When Planck tried to explain to Hitler that expulsion of Jewish scientists would be harmful to German interests, Hitler replied “then we shall do without science for a few years.”