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Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography


Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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 Quantum Effects
  video  - Photoelectric Effect in Zinc
 Stopping Potential
 Photoconductor (resistor)
  video  - Electron Diffraction
 Quantum Levitation (Flux Pinning)
 Atomic Physics
 Nuclear Physics

 video  - Photoelectric Effect in Zinc


To show that ultraviolet (UV) light of sufficient energy incident on a Zinc plate will cause electrons to be emitted from the metal's surface.


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  DEMO VIDEO DOWNLOAD / no audio / 1920x1080 / 24.19Mb/s / 460MB size  

  DEMO VIDEO DOWNLOAD / no audio / 854x480 / 5.69Mb/s / 109MB size  

Simulation: JavaLab Photoelectric Effect 2

Electrically connect the Zinc plate to the top of the electroscope via banana plug wire and charge (by touching plate) with the negative Teflon rod (rubbed with silk) so that there is a noticeable displacement of the electroscope leaves or arm. Place the UV light above the Zinc plate and turn it on. The loss of charge due to photoelectric emission can be seen by watching the electroscope leaves fall back to a vertical position. Note: the UV light source has short-wave (sw = 254nm) and long-wave (lw = 366nm) settings. Only at the sw setting electrons will be emitted from the Zinc plate).


The work function for zinc is approx. 4.31 eV which gives a cutoff wavelength of 288 nm.

Zinc surface should be cleaned with steel wool before use.


  • Electrometer
  • Silk
  • Teflon Tod
  • Zinc Plate w/ banana clip
  • Plexiglass Rod