The Crookes Radiometer

The Crookes radiometer is a device that shows how light energy can produce motion. It consists of a glass bulb with a partial vacuum, containing a rotor with four blades that are black on one side and silver on the other. When exposed to light or heat, the black sides absorb more energy, causing gas molecules near them to heat up and move faster. This creates tiny pressure differences that push the blades, causing the rotor to spin. The radiometer demonstrates how energy from light can be converted into mechanical motion, illustrating principles of heat, light absorption, and gas behavior.