Crooke's Radiometer (4D20.10)

Description:

A partially evacuated glass bulb holds a pinwheel where the vanes are reflective on one side and painted black on the other. Light from an incandescent lamp will be absorbed by the dark side of the vanes, heating the nearby air, and causing the pinwheel to rotate towards the reflective side of the vanes.

Procedure or Operation Notes:

This is verified by the second apparatus where the reflective/absorptive pattern on the vanes is reversed. When illuminated from the same light source, both radiometers rotate away from the absorptive side of the vanes.

References, Comments, or Footnotes:

1) Crooke's Radiometer [Wikipedia].