Crookes radiometer
Noun
Meaning
electromagnetic radiometer consisting of a small paddlewheel that rotates when placed in daylight
Source: WordNetHypernyms
Examples
The Crookes radiometer turns when the MFP is larger than the size of the vanes.
The first experiment to test this theory was done by Arthur Schuster in 1876, who observed that there was a force on the glass bulb of the Crookes radiometer that was in the opposite direction to the rotation of the vanes.