7A10.10 – Photoelectric Effect with Neon Bulb

Description: This shows the photoelectric effect.
If you shine the UV light on a near powered neon light, the charge will induce the light (indicated by the light turning on).
This is due to the photoelectric effect, whereby certain frequencies of light excite the electrons in certain metals.


  • Variac
  • 2 alligator clips
  • UV light source
  • Flashlight
  • Neon bulb

Setup Procedure:

  1. Plug the variac into the wall
  2. Attach the alligator clips to the banana clips attached to the variac
  3. Attach the alligator clips to each end of the neon bulb
  4. Set the variac power to just under the power needed to light the bulb

Demonstration Procedure:

  1. Power the variac on
  2. Shine the UV flashlight on the neon light, and the neon light should shine
  3. When finished, turn off the UV light and the variac