6A60.30-Projected Filament with lens

6a6030projected filarment with lens
Description: This demo projects the filament of a light bulb onto the screen using a Plano convex lens.


  • Large convex lens
  • Light bulb
  • VariAC
  • Box
  • Jack stand
  • VariAC to banana plug cable
  • (Optional) A second large convex lens
  • (Optional) Cardboard apertures and cardboard square

Setup Procedure:

  1. Place the jack stand inside the box. The box is used to shield students from the bright light.
  2. Connect the VariAC to the light bulb.
  3. Place the light on the jack stand.
  4. Set the VariAC to 120V
  5. Align the lens in front of the bulb. Focus the image on a screen or wall at the other side of the room. Slight adjustments to the lens may be needed to get a good image.

Demonstration Procedure:

  1. Turn on the VariAC.
  2. Turn off the room lights.
  3. Note the projected image of the light bulb filament.


  1. Use 2 large Plano convex lenses instead of one. Focus the image on the screen again.
  2. Using the cardboard apertures, you can show what happens when you limit the amount of light through the lens with different apertures.
  3. Using a cardboard square, block the bottom half of the outer lens. Note that the full image is still present. Repeat with blocking the top half of the outer lens.