| The Following Topics Might Appear on Exam 4 (2020) |
| Quantum mechanics: needed to describe very small physical systems |
| Definition of a small physical system: its size is about equal to the De Broglie wavelength of its particles or smaller |
| Simultaneity of events not absolute |
| Nothing can exceed the speed of light. |
| The speed of light is the same for all observers irrespective of their motion. |
| Length contraction (moving objects seem to contract in direction of motion) |
| Time dilation (moving clocks seem to slow down) |
| Gravitational Time dilation (the stronger the gravity at a clock's location, the slower it runs) |
| Relativistic mass (m = m0γ, moving masses seem to increase) |
| Principle of Relativity (Laws of phyics same in all inertial reference frames) |
| Speed of light the same in all inertial reference frames |
| Equivalence of mass and energy (E = mc2) |
| Photoelectric Effect (energy of ejected e- depends on frequency of light not its intensity) |
| Energy of photon (E = hf) |
| Frequency of photon an e- emits or absorbs in changing its energy level in an atom [f = (Ef - Ei)/h] |
| Key assumptions of Bohr atom: 2πr = nλ, λ = h/p |
| Dependence of Bohr atom's energy levels on n (En ~ -n-2) |
| Definition of coherent radiation (same phase, same frequency, same direction) |
| Stimulated Emission (photon of right frequency is "cloned" when it hits an excited atom ==> Laser light) |
| Compton Scattering Formula (X-rays act like particles with momentum p = h/λ. Wavelength of scattered X-ray depends on scattering angle) |
| De Broglie Wavelength of a particle (λ = h/p) |
| Quantum theory required to describe system when De Broglie wavelength of its particles ≥ size of system |
| Davisson-Germer Experiment (electrons act like waves in scattering from lattice according to Bragg's law) |
| Wave-particle duality (particles can act like waves, waves like particles) |
| Heisenberg Uncertainty Principle: For any particle, (uncertainty in position) X (uncertainty in momentum) ≥ h/(4π) |
| Schrodinger Equation (solutions explain atomic structure, energy levels) |
| Quantum numbers for electron in an atom [n (principal), l (angular momentum), ml (magnetic), s (spin)] |
| Possible values for quantum numbers 1 ≤ n < infinity 0 ≤ l ≤ (n-1) -l ≤ ml ≤ l s = ±1/2) [Caution: l = "el", 1 = "one"] |
| Pauli Exclusion Principle (two electons cannot have the same set of values for their quantum numbers) |
| Central Field Approximation (allows simple analysis of hydrogen atom to be applied to complex atoms) |
| Labels of subshells (l=0 → s, l=1 → p, l=2 → d, etc.) |
| Number of orbitals in a subshell = 2l + 1 = number of values of ml[Note: s, p, d, etc. are subshells. px, py, pz are orbitals of the p subshell.] |
| Max occupancy of a subshell = 2(2l + 1) = 2 x (number of orbitals) |
| Electron has a magnetic moment (i.e. it's a tiny magnet due its spin) |
| Zeeman Effect: Energy level splitting due external magnetic field. [The stronger this field, the stronger the splitting] |
| Spin-Orbit Effect: Slight energy level splitting due to the magnetic field produced by the motion of the nucleus (from the electron's point of view) |
| Meaning of Atomic Number (number of protons) |
| Constituents of nucleus (neutrons, protons) |
| Meaning of Mass Number (= number of protons + number of neutrons) |
| A nuclide is a nucleus that exists in nature or can be created artificially. |
| An isotope of a particular nucleus is another nucleus with the same atomic number and a different mass number. |
| Radioactive decay law (N = N02-t/T= N0e-λt where T = half life, λ=0.693/T) |
| Absorbed Dose [= (radiation absorbed)/(mass of tissue that absorbs it)] |
| Meaning of Relative Biological Effectiveness |
| Equivalent Dose = RBE x (Absorbed Dose) |
| Chief radiation risk to Americans (household radon) |
| Alpha Decay |
| Beta Minus Decay |
| Beta Plus Decay |
| Electron Capture |
| Gamma Decay |
| Nuclear Fission |
| Chain Reaction (at least 2 fast neutrons must result from each splitting. |
| Nuclear Reactions (mass numbers and atomic numbers balance) |
| Nuclear Fusion (fused nuclei have lower energy than when they were separated) |
| Mass Deficit = difference between mass of reactants and that of products |
| E = mc2, i.e. Nuclear reactions convert mass into energy: Reaction Energy = (Mass Deficit)×c2 |
| Carbon-14 Dating |
| Exothermic Nuclear Reaction (Reaction Energy > 0) |
| Endothermic Nuclear Reaction (Reaction Energy < 0) |
| Difference between a bomb and a reactor (controlled vs. uncontrolled fission) |
| The two pillars of modern physics [Relativity (special and general) & Quantum Theory] |
| Use quantum theory for very small systems, Special Relativity for very fast systems, and General Relativity for strong gravitional fields. |
| Exam will: |
| be closed book, closed notes. |
| be 25 questions |
| be 1 hour 15 minutes long |
| be multiple choice |
| allow calculators |
| not allow web-enabled devices |
| provide value of constants you might need |