Revise: Quantum and Atomic Physics
Thermionic emission and the vacuum diode, blackbody radiation and the photon, the historical models of the atom, atomic structure, and the structure and evolution of the visible universe.
Heating a metal releases electrons (thermionic emission). A vacuum diode conducts one way.
Old radio/TV tubes rectified AC to DC this way.
A blackbody's emission spectrum depends only on temperature.
A heated rod glows dull red, then white-hot.
Thomson → Rutherford (nucleus) → Bohr (quantized orbits).
Rutherford's alpha-scattering revealed the nucleus.
Z = protons. A = protons + neutrons. Isotopes: same Z, different A.
Z=17, A=35 → 17p, 18n, 17e.
Planet → star system → galaxy → galaxy cluster. Big Bang ~13.8 bn years ago.
Redshift shows distant galaxies moving away.
Current flows only when the anode is positive (attracts the electrons).
A negative anode repels electrons — no current.
Explaining this spectrum correctly led Planck to quantized energy — birth of quantum physics.
A star's color reveals its surface temperature.
Brightness = number of photons; color/frequency = energy PER photon.
UV photons carry more energy than visible light photons.
Each model was refined by NEW evidence the old model could not explain.
Thomson's model predicted no sharp deflections — disproved by Rutherford's data.
A neutral atom has equal protons and electrons.
Carbon-12 and carbon-14: same Z=6, different neutrons.
The Big Bang was the expansion of space itself, not an explosion at one point.
The cosmic microwave background is the leftover afterglow.