School of Physics Lecture Demonstration Manual

He-1 Crookes Radiometer

Published: Monday 13 March 2006 - Updated: Monday 28 March 2011

Aim

To demonstrate a sensitive detector of thermal radiation.

Apparatus

Diagrams

Click on pictures to enlarge.

Crookes radiometer Diagram

Description

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.

Safety notes

Electrical safety

Sharps Safety

Maintenance 

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