Physics 102: Modern Physics

Text: Modern Physics by Randy Harris

Chapter 3: Waves and Particles I: Electromagnetic Radiation Behaving as Particles

Photoelectric Effect This demonstration shows that certain wavelengths of light can push electrons from the surface of photoemissive solids by showing a charged plate lose charge when lit with a UV light.

Photocell This demonstrates a physical application to the photoelectric effect. When photons bombard a photoemissive material a small current is induced. This current can power a small lightbulb or other electronics. The actual mechanism of creating a current changes for different types of photocells (photoconductive vs. photoemissive vs. photovoltaic cells)

Maltese Cross A fluorescent screen is illuminated by a beam of electrons. A Maltese cross is put in the path of the electron beam and a shadow is produced on the fluorescent screen, showing the particle nature of electrons. A bar magnet can be used to show distortions in the path of an electron beam as it will distort the image created on the screen.

Chapter 4: Waves and Particles II: Matter Behaving as Waves

Electron Diffraction Apparatus This is a demonstration of electrons acting as a wave. The fluorescent screen shows interference patterns of an electron beam shone through a sheet of graphite, which acts as a grating.

Chapter 9: Statistical Mechanics

Thermoelectric Converter; Thermocouple This demonstration shows that a change in temperature of two conducting materials can create a potential difference that causes a current to flow.

Miscellaneous Demonstrations

Fluorescent Materials This demonstration shows that when exposed to high-energy light (UV), electrons in fluorescent materials can jump to higher energy levels and then fall back down. In this process there are photons released by the electrons cascading down that cause the material to emit light in the visible spectrum (even though the light source used to “charge” the electrons is not itself in the visible range).

Superconductivity This demonstration shows the Meisner Effect: superconductors expel all magnetic flux from within their volume. The result of this is that a permanent magnet will float above the superconducting material as long as it stays cold enough.