| <Previous | January | February | March | April | May | Next> |
Lecture 13: Beyond Classical Physics: Photons and Wave-Particle Duality
March 5, 2026
Reading Assignment
- Read: Supplementary Reading Ch 2
Objectives
- (Continuing objective) Describe applications of the concepts of induction, waves, and light to everyday “real life” situations.
- Describe the failures of classical physics in resolving the ultraviolet catastrophe, the stability of atoms, and the atomic spectra.
- Calculate any of these photon properties, given one of the others: energy, momentum, frequency, and wavelength. Solve problems relating light intensity, the number of photons per second, the energy per photon, and the frequency or wavelength of the associated wave.
- Explain how photons resolve the ultraviolet catastrophe, and calculate the number of photons in modes of a cavity in thermal equilibrium at temperature \(T\).
- Describe how light interacts with matter in the form of photons, and how this explains the photoelectric effect, ionizing radiation, and radiation-induced chemical reactions. Relate the photon energy, binding energy, and final kinetic energies of any freed electrons.
- Calculate the de Broglie wavelength for photons and for non-relativistic particles. Conversely, calculate the momentum or kinetic energy of a non-relativistic particle from the de Broglie wavelength.
Homework
- Friday's Assigned Problems:
Supp CH 2: 1, 3, 4, 5, 6, 7, 9, 10, 13, 14
Notes: For Supp CH 2 #5, answer in both eV/c and kg$\cdot$m/s.
- Monday's Hand-In Problems:
Supp CH 2: 2, 8, 11, 12, 15
Note: This is only the second half of the hand-in set.
Lecture Materials
- Click here for the Lecture overheads. Answers: CT1 - 2; CT2 - 6; CT3 - 6
- Video of the electron double slit experiment.
- PheT simulation of the photoelectric effect (requires java).
Videos of example problems
To see the problem statement, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement.- Example with electron microscope -- de Broglie's relation and diffraction limits
- Example of calculating how many photons are in a laser beam.
- Example of photons breaking apart something (in this case, breaking apart a molecule of water, similar to photoelectric effect problems.
- Example of using the Equipartition theorem to determine how many photons should be in a box, similar to the UV Catastrophe probelems.
Pre-Class Entertainment
- Got to Be Real - Cheryl Lynn
- Wild Night - Van Morrison
- 06 54 46, That's My Number - Toots and the Maytals
- Best of My Love - The Emotions
- Higher Ground - Stevie Wonder