He-1 Crookes Radiometer
Published: Monday 13 March 2006 - Updated: Monday 28 March 2011
To demonstrate a sensitive detector of thermal radiation.
- Crookes radiometer
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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.