Modern Physics

7A - Quantum Effects

10. Photoelectric Effect

7A10.1 Discharging by Photoelectric Effect
A zinc plate is attached to an electroscope (projected onto the screen) and charged with rubber and fur (negative charge). A small UV lamp is held near the plate and the electroscope steadily discharges. If, however, the zinc plate is charged positively with lucite and silk, the effect vanishes.
[Set-Up Time: 10 min.]
[Current Condition: good]

30. Band gaps

7A30.10 LEDs in Liquid Nitrogen
Bright LEDs of various colors are dunked in liquid nitrogen. Dramatic color changes, and increased brightness, are visible.
[Setup time: unknown]
[Current Condition: good]

50. Wave Mechanics

7A50.20 Microwave Barrier Penetration
3cm microwaves are totally internally reflected inside a wax prism. When a second wax prism is brought nearby, some of the beam tunnels across the air gap and is transmitted. Two detectors are used to show that as more of the signal tunnels and is transmitted forward, the reflected signal diminishes.
[This demo has no standard setup because it is still being tweaked.]
[Current Condition: good]

7A50.40 Vibrating Circular Wire
A hoop of wire is excited at audio frequencies to show standing waves on a domain with periodic boundary conditions.
[Set-Up Time: 10 Min.]
[Current Condition: good]

60. X-ray and Electron Diffraction

7A60.50 Bragg diffraction with microwaves - improved apparatus
X-ray crystallography scaled up to centimeter wavelengths. The microwave source and detector are constrained to the same angle of incidence, which can been easily read off the device. The detector is attached to an audio speaker, through which the detected amplitude can be heard. As the beam angle is varied, or the crystal is rotated, distinct peaks are audible. A cubic crystal is currently available; different structures can be made upon request.
[Setup time: 10 mins.]
[Current Condition: Good]

7B - Atomic Physics

10. Spectra

7B10.1 Line Spectra and Student Gratings
Hydrogen and Helium discharge tubes, as well as an incandescent lamp, are viewed through simple gratings. There are about thirty or forty gratings that can be distributed to the students.
[Set-Up Time: 10 min.]
[Current Condition: Good]

7B11.17/21 Absorption Spectra
Two lamps show different absorption phenomena. In one bulb, neodymium oxide in the glass absorbs a band in the yellow; in the other, sodium vapor around the bulb absorbs the yellow spectral line. Students observe the spectra through diffraction glasses.
[Set-Up Time: 5 min.]
[Current Condition: Good]

13. Resonance Radiation

7B13.50 Fluorescent UV Beads
Special beads appear white, but they fluoresce bright colors when exposed to UV light.
[Setup time: 5 mins.]
[Current Condition: Good]

30. Ionization Potential

7B30.1 Franck-Hertz Experiment
Demonstrate that mercury atoms are excited only in discrete energy quanta by accelerating electrons through a tube containing mercury vapor, and observing the current of electrons striking the opposite side of the tube as a function of the accelerating voltage. See 7B30.1 Franck-Hertz Experiment in the Technical Pages for a more detailed description.
[Set-Up Time: 40 min.]
[Current Condition: Good, please allow for a large amount of setup time]

7D - Nuclear Physics

10. Spectra

7D10.10 Geiger Counter and Samples
Listen to a Geiger Counter when radioactive samples are tested. Beta and Gamma sources are available.
[Set-Up Time: 5 min.]
[Current Condition: Good]

30. Particle Detectors

7D30.63 Lecture Hall Cloud Chamber
A large diffusion cloud chamber is filled with supersaturated alcohol vapor that is cooled by liquid nitrogen or dry ice. The resulting cloud forms condensation trails along the path of charged particles. The best way to "see" cosmic rays and other ionizing radiation. Includes a port for an alpha particle source.
[Set-Up Time: 20 min. Best for classes in 301]
[Current Condition: Good- works about 50% of the time. please allow for long setup time]

7F - Relativity

10. Special Relativity

7F10.1 Special Relativity - Video
Three 3-5 minute segments from the Mechanical Universe video series demonstrate: the relativity of simultaneity, time dilation, and space-time Minkowski diagrams. Compelling and easy to understand animations.
[Set-Up Time: 15 min.]
[Current Condition: Unknown]
This is the same video:
go to episode 42: The lorentz transformation. Make sure you allow popups, and click the VoD icon to the right
the video will appear in a new window, and the relevant portion is ~8 minutes in.

20. General Relativity

7F20.1 Black "Chalk" Globe
Draw a triangle on a globe with chalk to demonstrate an example of non-Euclidean geometry.
[Set-Up Time: 2 min.]
[Current Condition: Good]