For an explanation, see the main splats page
SPLATS about quantum physics
The principles of quantum physics
- The photoelectric effect was dependent on wavelength but not on intensity of the light, a puzzle that led to the discovery of what we now call quantum physics.
- Blackbody radiation was explained when quantum physics was developed, because it solved a number of apparent paradoxes about the energy of radiation.
- The 'violet catastrophe' said that if all frequencies are equally likely from a hot body, the many wavelengths beyond violet should swamp any emission spectrum.
- The 'violet catastrophe' does not occur, and unless the body is very hot, we do not even see any red light emitted from it, let alone violet or ultraviolet.
- Kirchhoff wanted to know why this was so. Because the higher frequencies are unlikely unless the body has very high energy, answered Planck's little equation.
- Wien produced a formula which explained the distribution of energy in a radiation spectrum as a function of both wavelength and the temperature of the body.
- Wilhelm Wien's displacement law explains why the sun's radiation peaks in the region we see best, because the sun has a surface temperature of around 6000 K.
- Wien's formula worked well at short wave-lengths, but failed at longer wave-lengths. Rayleigh's formula accurate at longer wavelengths but not at shorter ones.
- Rayleigh came up with a theory of black-body radiation, later modified by James Jeans, and often known as the Rayleigh-Jeans Law or the Rayleigh-Jeans theory.
- Sir James Jeans demonstrated the classical formula for the partition of radiant energy in an enclosure, which we now call the Rayleigh-Jeans Law.
- Linked to the displacement theory of Wilhelm Wien, the Rayleigh-Jeans Law more or less explained black-body radiation, until Max Planck found a better answer.
- In 1900, Max Planck proposed basic quantum theory, involving light quanta in black body radiation, Planck's black body law and Planck's constant.
- Planck saw that if the radiation was emitted only in 'packets' of a minimum energy, he could calculate a radiation law which was good for all wavelengths.
- In 1901, Max Planck made determinations of Planck's constant, Boltzmann's constant, Avogadro's number and the charge on the electron, all in one year.
- Later, Albert Einstein explained the photo-electric effect from Planck's work. A shorter wave-length photon had more energy, and so could dislodge an electron.
- In 1925, Walter Elsasser explained electron diffraction by regarding it as wave property of matter, further smearing the wave/particle distinction.
- Quantum mechanics is a mathematical description of quantum effects, relating to the way in which, on a small scale, variables cease to be continuous.
- Quantum physics has given us the interesting paradox of Schrödinger's Cat, which is a sort of thought experiment which appears to show a contradiction.
- When electrons move from one shell to another, they absorb or emit a specific amount of energy related to that shift, producing lines in a spectrum.
- The energy absorbed when electrons move to higher levels make part of the absorption spectrum, each transition contributing a single line to the spectrum.
- The energy emitted when excited electrons move to a lower level makes the emission spectrum of that atom: each shift contributes one line to the spectrum.
- So far, gravitation has not been incorporated into quantum theory, but that remains a hope and a goal for physicists researching in that area.
- The Heisenberg uncertainty principle indicates that not all measurements may be made simultaneously. It is widely misunderstood and misquoted.
- Wigner's friend is a variant on Schrödinger's Cat. The 'friend' is a human observer who replaces the cat in one of the thought experiments on quantum reality.
- In 1926, Erwin Schrödinger derived the spectrum of hydrogen atom using the wave equation, reinforcing the notion that waves and particles are interchangeable.
- In 1926, Schrödinger also showed the wave and matrix formulations of quantum theory were mathematically equivalent, combining the two sides of quantum physics.
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