ASRJC Quantum Physics

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 19-1 Additional Notes Topic 19: Quantum Physics Content: A The energy of a photon and the photoelectric effect B Wave-particle duality C Energy levels in atoms D Line spectra E X-ray spectra F 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 E = hf for the energy of a photon (c) show an understanding that the photoelectric effect provides evidence for a 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 ½ mvmax2 = eVs, where Vs is the stopping potential. (f) explain photoelectric phenomena in terms of photon energy and w ork 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 hf =  + ½mvmax2 (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 (k) show an understanding of the existence of discrete electron 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 by 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 ∆ρ∆x ≳ h as a form for the Heisenberg position-momentum uncertainty principle to new situations or to solve related problems. Lecture SOW Lect Concepts Questions Est. Video Time 1 A.1 – A.4 CYU1 38 min 2 A.5 – A.8 CYU2, CYU3 and Example 1 41 min 3 B.1, B.2 and C Example 2, Example 3, Example 4, CYU 4 40 min 4 C.1 - D.3 CYU5 and CYU6 37 min 5 E.1 – E.3 Example 5, Example 6 37 min 6 F Example 7, Example 8 and Example 9 14 min

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 19-2 Additional Notes • In earlier topics we learnt that phenomena such as interference and diffraction are exhibited by light as it is passed through slits in Young’s double slits experiment. • These observations provide evidence for a wave nature of electromagnetic radiation. • However, when we look at observations associated with the photoelectric effect, we discover a completely different aspect of light. • We find that the energy of electromagnetic radiation is quantized; it is emitted and absorbed in particle-like packages of definite energy. A.1 The Experimental Setup