He-1 Crookes Radiometer


To demonstrate a sensitive detector of thermal radiation.


  • Crookes radiometer
  • Desklamp

Crooke's Radiometer 1

Crookes Radiometer.


The radiometer consists of four light mica vanes blackened on one side and silvered on the other and arranged on a common pivot so that they may rotate freely in a horizontal plane. The glass container is evacuated to a pressure of approximately 10 mm of mercury. At this pressure there are still many gas molecules to interact with the vanes and the mean free path is large.