EJC Physics H219 (2024) - 1. Quantum Physics Notes (FULL)

Page 1 of 36 9749(2024) H2 Physics H219 Quantum Physics Notes H2 Topic 19 Quantum Physics The Nobel Prize in Physics 1921 was awarded to Albert Einstein " for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect." Content • Energy of a photon • The photoelectric effect • Wave-particle duality • Energy levels in atoms • Line spectra • X-ray spectra • The uncertainty principle Learning Outcomes Candidates should be able to: (a) show an appreciation of the particulate nature of electromagnetic radiation (b) recall and use the equation E = hf for the energy of a photon (c) show an understanding that the photoelectric effect provides evidence for the particulate nature of electromagnetic radiation while phenomena such as interference and diffraction provide evidence for the wave nature (d) recall the significance of threshold frequency (e) recall and use the equation 2 max s 1 2 mv eV= , where VS is the stopping potential (f) explain photoelectric phenomena in terms of photon energy and work function energy (g) explain why the stopping potential is independent of intensity whereas the photoelectric current is proportional to intensity at constant frequency (h) recall, use and explain the significance of the equation 2 max 1 2h mvf Φ+= (i) describe and interpret qualitatively the evidence provided by electron diffraction for the wave nature of particles (j) recall and use the relation for the de Broglie wavelength λ = h / p (k) show an understanding of the existence of discrete electronic energy levels in isolated atoms (e.g. atomic hydrogen) and deduce how this leads to the observation of spectral lines (l) distinguish between emission and absorption line spectra (m) recall and solve problems using the relation hf = E2 – E1 (n) explain the origins of the features of a typical X-ray spectrum (o) show an understanding of and apply ΔpΔx ≳ h as a form of the Heisenberg position-momentum uncertainty principle to new situations or to solve related problems.

Page 2 of 36 9749(2024) H2 Physics H219 Quantum Physics Notes 19.1 Particles and waves We often model matter using particles (small masses) that are hard, rigid and move according to Newton’s Laws of motion. The macroscopic phenomena can then be explained by the random motion and collisions of the distribution of particles. area microscopic model macroscopic phenomena typical diagrams electricity flow of electrons current gases Kinetic Theory pressure, volume, and temperature of gas solids lattice structure mechanical properties On the other hand, waves are used to explain the transport of energy without matter being transported. The medium of transport is often described as oscillating. area oscillating quantity typical diagrams sound air pressure light (electromagnetic radiation) electric field and magnetic field waves on a string displacement (of strin