Kaplan MCAT Physics Ch. 11: Atomic Phenomena
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sportyperson246 on July 5, 2012
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34 terms
Terms | Definitions |
|---|---|
 ideal radiator => blackbody | ideal radiator is also ideal absorber and would appear totally black if temp lower that surroundings, since absorb all wavelengths of EM radiation |
| cavity radiation | radiation produced in cavity w/in hot object blackbody radiator can be approx. to this |
| Planck's formula | for blackbody, one wavelength at which max. amount of energy is emitted (peak) depends on abs. temp of body in relation to Wien's displacement law cooler => radiates less energy => other object has higher abs. temp |
| Wien's displacement law | (peak)(T) = constant |
| (peak) | more energy is emitted than at any other wavelengh, but doesn't refer to max. wavelength emitted |
| Stefan-Boltzmann law | total energy emitted per sec per unit area (W/m^2) prop. fourth power of abs. temp inc. abs temp => inc. intensity => peak wavelength dec. |
| photoelectric effect | light => freq => metal => emit electrons => net charge flow per unit time, or current all or none response |
| threshold frequency (fT) | min. freq. of light that causes ejection of electrons depends on type of metal light quanta (photons) => energy of each prop. to freq. of light E = hf h= Planck's constant high freq => shorter wavelength => higher energy (same for vice versa) common units = nm and angs |
| wavelength | if know freq, can solve for this =c/f c = speed of light |
| max. KE | if freq. of photon on metal at threshold => electrons barely escape more that enough energy => eject => excess energy converted to KE of ejected K = hf - W |
| work function (W) | function of min. energy required to eject electron related to threshold freq of that metal W = hf(T) |
| freq. pattern in photoelectric effect | freq < thres. freq => no electron ejected freq. > thres. freq => ejected and KE equal to diff. between hf and hf(T) |
| current pattern in photoelectric effect | freq above thres. => light greater intensity => greater current (current prop. to intensity of light higher intensity => greater # photons per unit time => greater electrons eliminated |
| photoelectric effect on devices for visibility in low-level light | detect low intensity ambient light (reflected by object being viewed) => amplify weak light => each photon => detector plate => eject electrons (electric field accelerates) => emits light => bright image |
| bohr model of H atom | electron around circular orbit centripetal force acting on electron as it revolves around nucleus = electrical force between + charged proton and - charged electron |
| Energy Level (H atom) | orbital angular momentum of electron => energy of electron electron changes only in discrete amounts w/ respect to quantum number specific stable, or allowed, orbits of quantized (discrete) energy in which electrons did not radiate energy => energy level formula energy levels of H given in eV |
| bohr energy | in eV corresponds to closet orbit to nucleus is -13.6 eV energies farther away => less neg => greater => free from electrostatic (coulombic) => pull nucleus => positive energy (ionization) 0 energy => P and E separately completely => no attractive forcse positive energy states => no principle quantum number => E not bound to P => free energy state => electron in quan. states => neg energy => attractive energy of electron inc. farther from nucleus n^2 inc => value inc. |
| quantized energy | thought of change in GPE => change in height => discrete (quantized) changes of PE |
| orbit | transferring an amount of energy exactly equal to difference in energy between on pathway to another |
| ground state | smallest radius from nucleus |
| excited state | higher energy orbit |
| orbital angular momentum of electron => | L = nh/2pi |
| energy of electron | E = -R(H)/n^(2) |
| energy levels of H in eV | E(n) = -13.6 eV/ n^(2) |
| 4 postulates of Bohr model | 1. Energy levels are stable and discrete, specific orbits 2. Electrons emits or absorbs when transition from one energy level to another 3. jump lower => higher; electron absorb a photon of precisely right freq. that photon energy (hf) equal energy diff. between two orbits 4. jump higher => lower; electron emits a photon of freq. such that photon's energy (hf) exactly energy difference between two orbits |
| change in electron's energy | electron in lowest allowed energy level can't emit any more energy (although could absorb radiation and jump to higher) E(f) - E(i) |
| Electron in excited state can either emit radiation when | jumps down to lower energy or absorb radiation when it jumps to higher |
| emission of photon that has frequency | bound-state energy levels are neg. if E is neg. electron (neg) from higher, less neg. energy state (less tight bound state) to lower, more neg. energy state (more tightly bound state) hf = -E |
| absorbed photon has freq. | E is pos. electron from lower, more neg to higher, less neg energy |
| fluorescence | excite fluorescent substance w/ UV radiation => glow w/ visible light UV radiation photons => high freq. (short wavelength) => after exciting higher energy state => electrons original in two or more steps (each less energy and lower freq (longer wavelength)) => if wavelength w/in visible range => light of particular color |
| energy of photons | inc w/ increasing freq. |
| energy of photons | converted into ejecting electron (amount required by work function will be given in problem), and any excess energy is converted into KE |
| negative frequency | no such THING |
| Planck's constant | h = 6.63 x 10^-34 J x s = 4.14 x 10^-15 eV x s |
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