Radiometer, 1 Each

United Scientific® Radiometer by United Scientific is a partially evacuated glass bulb holding a four-vane rotor on a low-friction spindle, with each vane blackened on one side and silvered on the other. Under sunlight or artificial light the vanes turn because of differential heating, and a white dot on one vane makes rotation counts easy. Science teachers use it for classroom demonstrations of electromagnetic radiation and energy conversion.