Chem 202 - Webtext 2.6
Math / Symbols
|Albert Einstein's equation relating mass and energy|| E² = m²c⁴ + p²c²|
The equation is so often turned into E=mc² because for a massed particle, the momentum is so small that the p²c² term is negligible.
|Photons||Light energy comes in small packets of well-defined energy called photons.|
|Photons vs. Electrons||Photons are electrically neutral, have no mass, and have a spin of 1, not ½.|
|Photons and the Pauli exclusion principle||Photons do not obey the Pauli exclusion principle; they are gregarious particles.|
|Energy for a free particle|| Energy = mass-energy + kinetic energy.|
For a non-free particle, add the potential energy (i.e. the p²c² term).
|Energy of a photon|| A photon is massless, so its energy is given by|
E = pc
|p = h / λ||A Fourier principle that holds as a special case for freely moving particles such as photons or electrons not stuck in a box; hence, the wavelength of the particle replaces the length of the box.|
|Waves and quantum particles||The Heisenberg priciple, with its Fourier-conjugate relationship between momentum and distance, imparts on quantum particles properties usually reserved for waves.|
|Planck's Law|| E = hν|
The energy of a photon is linearly proportional to its frequency.