1. Chapter 3 Light at Particles

2. Blackbody Radiation

3. Light waves Interference Diffraction Maxwell’s Equations Ether?

4. Blackbody Radiation Hot things radiate more energy (Stefan- Boltzmann Law) –E =  T 4 –P =  A T 4  = emissivity (0-1, “how good of a blackbody”)  = 5.67 x 10 -8 W/m 2 K 4 Hot things have a measureable spectrum The spectrum shifts depending on temperature –Wein’s Law (1893)  max = b/T –b = 0.002898 m K

5. Blackbody Radiation thought experiment Radiation is absorbed through a hole and creates a long-lived standing wave. Eventually, a light wave escapes and can be detected. A furnace at very high temperature

6. Blackbody Radiation Lord Rayleigh (John William Strutt) derived a classical expression based on standing waves

7. Lord Rayleigh’s Derivation Thermal Physics –Equipartition Theorem Energy/wave = ½ k B T Ultraviolet Catastrophe kBTkBT kBTkBT kBTkBT kBTkBT kBTkBT kBTkBT kBTkBT............

8. Wilhelm Wien Spectrometers worked well at small wavelength (large frequency) Was able to derive a formula that worked in this range I  f 3 e -af/T –f : frequency –T : temperature –a : constant

9. Max Planck Quantized energies –E = 0, hf, 2hf, 3hf, … = nhf n : energy quantum number Ludwig von Boltzmann “… an act of desperation… a theoretical explanation had to be found at any cost, whatever the price…”

10. Distribution Comparison

11. Cosmic Background T = 2.727 K f = 160.2 GHz = 1.06 cm

12. Various Evaluations Wave TypeFrequency (Hz)WavelengthT(K) gamma10 21 0.3 pm1.76 x 10 10 X-Ray10 18 0.3 nm1.76 x 10 7 UV10 15 300 nm17,600 VIsible6 x 10 14 500 nm11,000 IR10 14 3 µm1760 microwave10 3cm0.176

13. Photoelectric Effect Wave description of light by Maxwell –Light intensity should determine whether an electron is ejected –Electric field vibrates the electron loose if there are enough waves (high intensity) to jiggle it loose.

14. Photoelectric Effect James Clerk Maxwell –EM waves traveling at c (1885) Heinrich Hertz –Sparks created from light hitting metal electrodes (1886-87) Wilhelm Hallwachs Clean charged metal surfaces (1888) - - - - - -

15. Photoelectric Effect J. J. Thomson –Discovered that the particles ejected were electrons (1899) –Cathode ray tube Philipp Lenard –Hertz assistant –Cathode tube (1902) Intensity Wavelength Albert Einstein –Theory to describe photoelectric effect (1905)

16. Photoelectric Effect Albert Einstein –Theory to describe photoelectric effect (1905) –Photons are packets of kinetic energy –Nobel 1911

17. Photoelectric Effect Robert Millikan –Surface cleaning in-situ –Disagreed with Einstein’s theory –Experiments to verify Einstein’s eqn –Measured Planck’s constant, h, to within 0.5% MetalWork Function (  ) Cs1.9 eV K2.2 eV Na2.3 eV Mg3.7 eV Zn4.3 eV Cr4.4 eV W4.5 eV Conservation of energy KE = hf -  h = 6.626 x 10 -34 J s

18. Photoelectric Effect Einstein’s relationship gave a nice linear way of determining Planck’s constant MetalWork Function (  ) Cs1.9 eV K2.2 eV Na2.3 eV Mg3.7 eV Zn4.3 eV Cr4.4 eV W4.5 eV Conservation of energy KE = hc/ -  Cs Mg W

19. Photoelectric Effect Einstein’s relationship gave a nice linear way of determining Planck’s constant MetalWork Function (  ) Cs1.9 eV K2.2 eV Na2.3 eV Mg3.7 eV Zn4.3 eV Cr4.4 eV W4.5 eV Conservation of energy KE = hf -  Cs Mg W

20. Multichannel Plate – Light Amplification by PE effect - + lens Phosphorescent screen Incoming light PE metal Amplified electrons photoelectron

21. X-Ray Production Bremsstrahlung: “Braking Radiation”

22. X-Ray Production

23. Compton Effect – 1927 Nobel

24. Blackbody Radiation

26. Wien Distribution

27. Blackbody Radiation

29. Probability (a brief diversion)

31. P(2) P(3) P(4) P(5) P(6) P(7)

32. Probability (a brief diversion) P(12) P(11) P(10) P(9) P(8)

33. Probability (a brief diversion)

35. Planck Distribution

38. Solar Spectrum Incorrect Solar Spectrum from only changing x-axis (  =hc/ ) 

39. Photoelectric Effect

43. Compton Effect

47. Compton Effect w/ long

48. Limiting Cases

49. Pair Production Carl D. Anderson (1905 -1991) –Nobel Prize for the discovery of positrons 1936 –Discovered the muon in 1936 –Worked for Robert Millikan

50. Pair Production

55. Particle vs. Wave

58. Diffraction & Interference

60. Double Slit Experiment 10 (a), 200 (b), 6000 (c), 40000 (d), 140000 (e).

61. Matter Waves 1924 doctoral thesis –Approved by Einstein 1929 Nobel

62. Particle vs. Wave

64. Compton Effect