Which of the following energy diagrams correctly describes the photoelectric effect? (A) (B) (C) Ekin hn F F hn Ekin F hn Ekin Ekin is the kinetic energy of the emitted electron F is the work function of the surface hn is the photon energy

Which of the following energy diagrams correctly describes the photoelectric effect? (A) (B) (C) Ekin hn F F hn Ekin F hn Ekin Ekin is the kinetic energy of the emitted electron F is the work function of the surface hn is the photon energy

+ Which of the following ideas for the H atom makes most sense to you? (A) Electrons are discrete particles embedded in a smeared out positive background charge. (B) Electrons orbit the nucleus just like the planets orbit the sun. In principle, their orbit can have any radius. (C) Electrons move on circular orbits around the nucleus, but they are only allowed to have certain radii. (D) Electrons don’t actually orbit the nucleus. Their positions and momenta cannot be predicted exactly. + - - - - - - - - - - -

+ Which of the following ideas for the H atom makes most sense to you? (A) Electrons are discrete particles embedded in a smeared out positive background charge.  Thompson’s “Plum Pudding” (B) Electrons orbit the nucleus just like the planets orbit the sun. In principle, their orbit can have any radius.  Rutherford’s Planetary Model (C) Electrons move on circular orbits around the nucleus, but they are only allowed to have certain radii.  Bohr’s Model (D) Electrons don’t actually orbit the nucleus. Their positions and momenta cannot be predicted exactly.  Schrödinger Equation + - - - - - - - - - - -

What would you expect for the trajectories of the -particles according to Thompson’s Plum Pudding Model? ... They all fly straight through the Au foil with very little deviation, if at all. (B) ... They are all bounced back, because the Au foil is too thick. (C) ... Most of them fly straight through, but some of them are scattered back at large angles J. J. Thomson (1856-1940)

What would you expect for the trajectories of the -particles according to Thompson’s Plum Pudding Model? ... They all fly straight through the Au foil with very little deviation, if at all. (B) ... They are all bounced back, because the Au foil is too thick. (C) ... Most of them fly straight through, but some of them are scattered back at large angles J. J. Thomson (1856-1940)

L r The Rutherford Model of Atoms Based on the idea that electrons circle the nucleus on classical orbits, formulate a relationship between the motion of the electron and the interaction between electron and nucleus. (A) The gravitational interaction between electron and nucleus must balance the centrifugal force. (B) The kinetic energy of the orbiting electron must be the same as the potential energy coming from Coulomb attraction between nucleus and electron. (C) The force keeping the electron on the orbit must equal the Coulomb force. (D) Linear momentum must be conserved. (E) … (B) and (C) mean the same thing, anyway, and they are both correct. L F r v

L r The Rutherford Model of Atoms Based on the idea that electrons circle the nucleus on classical orbits, formulate a relationship between the motion of the electron and the interaction between electron and nucleus. (A) The gravitational interaction between electron and nucleus must balance the centrifugal force. (B) The kinetic energy of the orbiting electron must be the same as the potential energy coming from Coulomb attraction between nucleus and electron. (C) The force keeping the electron on the orbit must equal the Coulomb force. (D) Linear momentum must be conserved. (E) … (B) and (C) mean the same thing, anyway, and they are both correct. L Gravitation plays no role here F r No. In fact, Ekin = -1/2 Epot v Only in absence of external forces!