Chad provides an introduction to Quantum Physics describing three areas where classical physics was insufficient to explain reality: Blackbody Radiation, the Photoelectric Effect, and the de Broglie Relation. Classical physics failed to explain the behavior of blackbody radiation at short wavelengths, termed the Ultraviolet Catastrophe. Classical physics predicted that the intensity of blackbody radiation should approach infinity as the wavelength approached zero. This was in direct contrast to the fact that the intensity went to zero as the wavelength went to zero. Max Planck was able to fit the data to equations that supposed that a blackbody was composed of harmonic resonators whose energy was quantized, i.e. whose energy could only have certain discrete values.
Later, Einstein presented a quantum model to explain the Photoelectric Effect, in which electrons are ejected from a metal with the shining of incident light. Classical theory, which viewed light as purely wavelike, could not explain why light had to be of a certain minimum frequency to eject any electrons regardless of how intense the beam. Einstein proposed that light also behaved like a particle (called photons) whose energy was proportional to its frequency rather than to its intensity as predicted by classical theory. Once again, a quantum model in which the energy of light is quantized, was able to fit the data, and the same constant (Planck's constant) that appeared in Planck's Equations for Blackbody Radiation appeared in Einstein's equations describing the Photoelectric Effect.
Finally, the de Broglie Relation predicted a certain symmetry in nature. Einstein had proposed that light was not only wavelike, but also particlelike in nature (WaveParticle Duality). de Broglie proposed that perhaps matter was not only particlelike, but also wavelike in its behavior. It has since been demonstrated for small particles like the electron, that they do indeed exhibit wavelike behavior.

00:00 Lesson Introduction
01:12 Blackbody Radiation
05:04 Photoelectric Effect
12:13 de Broglie Effect

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