Home Home Astronomy Chemistry Electronics Mathematics Physics Field Trips Home  

Experiment 8: Radiometer


9 December 2009 by Quest 2, to link in with Chapter 8 of our book.


To investigate the effects of sunlight on a Crookes radiometer.


Place a Crookes radiometer in the following locations and observe how fast the blades rotate.

  1. A shady place indoors.
  2. A shady place outdoors.
  3. A sunny place outdoors.
  4. A sunny place outdoors, but under a black light-proof cloth. Remove the cloth.

Materials & Equipment

  • A Crookes radiometer.


  1. The blades rotated slowly.
  2. The blades rotated quickly.
  3. The blades rotated so quickly they were a blur.
  4. The blades almost stopped completely under the cloth, and started spinning quickly as soon as the cloth was removed.


  • A Crookes radiometer is an effective device for getting a rough idea of the intensity of incident light.