1. Atomic and Nuclear Physics
Chapters 38-40

2. Wave-Particle Duality of Light
Young’s Double Slit Experiment (diffraction) proves that light has wave properties
So does Interference and Doppler Effect
Photoelectric Effect proves that light has properties of particles

3. Max Planck
From Planck’s work on Blackbody Radiation, he proposed that the energy of light is quantized
Quantization is an idea that energy comes in bundles or discrete amounts
Energy is quantized
This idea disagreed with established (traditional) physics

4. Photoelectric Effect
Light shining on a photo-sensitive metal plate will emit electrons.

5. Photoelectric Effect
Frequency must be above a minimum (threshold) frequency
Brighter light (higher intensity) produces more electrons, but with the same energy
Light with higher frequency will emit electrons with higher energy

6. Photoelectric Effect

7. Photoelectric Effect Law of Conservation of Energy must be followed
Energy must be related to frequency
Law of Conservation of Momentum must also be followed
Light has momentum

8. Photoelectric Effect
Einstein used Planck’s work to explain Photoelectric Effect (Nobel Prize 1921)
Proposed that discrete bundles of light energy are photons
Energy is proportional to Frequency
E=hf
h, Planck’s Constant
6.63 x J*s

9. Photoelectric Effect Conservation of Energy
Energy of Photon = Energy of ejected electron + work needed to eject electron (work function, Φ)

10. Photoelectric Effect

11. Photoelectric Effect
Maximum Kinetic Energy is measured by how much voltage (stopping voltage) is needed to stop electron flow
KEMAX = qV
1electron stopped by 1 Volt = 1.6 x 10-19J
1electron stopped by 1 Volt = 1eV

13. Compton Effect
1923 Arthur Compton uses photon model to explain scattering of X-rays
Determines equation for momentum of a photon

14. Compton Effect X-ray photon strikes an electron at rest
After the collision both the electron and X-ray photon recoil (move) in accordance with Laws of Conservation of Momentum and Energy
The photon transfers some momentum to the electron during collision.

15. Compton Effect
Change in wavelength of photon must be related to momentum
Magnitude of Photon Momentum:

16. de Broglie Wavelength
1923, graduate student, Louis de Broglie suggested that if light waves could exhibit properties of particles, particles of matter should exhibit properties of waves
Used same equation as momentum of photon

17. Davisson-Germer Experiment
Verified de Broglie’s idea of matter waves
Directed beam of electrons at crystal of nickel
Electrons showed diffraction pattern
Proof that particles have wave properties

18. Schrödinger’s Cat Thought Experiment about basis of quantum mechanics
Place cat, vial of poison, Geiger counter with radioactive sample in a seal box.
After 1 hour the cat is either alive or dead
Can’t know without interrupting the experiment (opening the box)
The cat is considered BOTH alive and dead

20. Atomic Models Dalton’s Model, early 1800’s Plum Pudding Model, 1904
Hard uniform sphere
Plum Pudding Model, 1904
After discovery of electron by J.J. Thomson
Rutherford Model, 1909
After Geiger Marsden Experiment

21. Atomic Models Bohr Model, 1913 Dense positive nucleus
Electrons moving in certain energy levels (orbits)

22. Quantum Mechanical Model
More detailed view of the Bohr Model
Schrödinger Wave Equation and Heisenberg Uncertainty provides region of high probability where electron COULD be.
Orbital
Modern Model

23. Energy Level Transitions
Electron energy is quantized
Electrons can move between energy levels with gains(absorption) or losses(emission) of specific amounts of energy.

24. Energy Level Transitions

25. Line Spectra Emission Spectra Absorption Spectra
Shows only the light that is emitted from an electron transition
Absorption Spectra
Shows a continuous color with certain wavelengths of light missing (absorbed)

26. Energy Level Transitions

27. Energy Level Transitions
Examples:
Calculate energy needed for transition from n=1 to n= eV
Calculate energy released by transition from n=5 to n= eV
What wavelength of light is this?
434 nm

29. Nuclear Physics Nucleus – center of atom Proton, p Neutron, n
Contains nucleons, protons and neutrons
Proton, p
Positively charged particle, 1e
m= x kg
Neutron, n
Neutral particle
m= x kg

30. Atomic Mass Unit Based on Carbon-12 atom 1u = 1.6605 x 10-27 kg
Proton mass = u
Neutron mass = u

31. Nuclear Reactions Fission and Fusion
Energy produced comes from mass being converted into energy (Mass Defect, Δm)

32. Mass-Energy Conversion
E=mc2
1 u = x J
1 u = 9.31 x 108 eV = 931 MeV

33. Fundamental Forces Strong Force Weak Force
Force that holds nucleons (protons and neutrons) together
Short range
Weak Force
Associated with radioactive decay
Short Range

34. Fundamental Forces Gravitational Force Electromagnetic Force
Attractive only
Long distance range (think planets)
Electromagnetic Force
Attractive and repulsive force on charged particles
Long range (think stars)

36. Classification of Matter
Matter is broken down into 2 types
Hadrons and Leptons
The Quark Family, also called Hadrons, are broken down into 2 types
Baryons and Mesons

37. Quarks Six quarks Up, Down, Top, Bottom, Strange, and Charm
Up, Charm, and Top all have +2/3 charge
Down, Strange, and Bottom all have -1/3 charge

38. Baryons Baryons are comprised (made of) three quarks
The total charge for any baryon is the net charge of the three quarks together
Examples:
uud = +2/3, +2/3, -1/3 = +1 = proton
udd = +2/3, -1/3, -1/3 = 0 = neutron

39. Mesons Mesons are comprised of a quark and its antiquark Antimatter
Particles that have the same mass but opposite charge of their matter partner
Have same symbol as matter but with added bar above symbol
Up quark, u up antiquark, ū

40. Leptons Leptons are separated into six flavours
Electron, Muon, and Tau all have -1 charge
Electron neutrino, muon neutrino, and tau neutrino all have 0 charge

41. Annihilation
When matter and antimatter particles collide, they annihilate each other and produce energy
E=mc2
kg  J (use equation)
u eV (use conversion on Reference Tables)