Crooke's radiometer with flashlight, arc lamp or IR source.

Crooke's Radiometer with white light source or IR source. Light from a flashlight,arc lamp, slide-projector, laser pointer or infrared source illuminates the Radiometer. The vanes of the Radiometer turn. The device has a slight amount of gas inside. Each vane is black on one side and silvered on the other.The black side absorbs IR and heats up, heating the adjacent gas. The temperature difference between the two vanes creates a convection from the light side to the dark side, and by Newton_s 3rd Law, the vanes move in the opposite direction. RADIATION.