Solar Radiometer

The Solar Radiometer transforms light energy into mechanical energy.  In a glass bulb under partial vacuum, on a low-friction needle point, are a set of black and white metal vanes.  Visible or infrared light causes a small difference in heat on each side of the vanes, which interact with the small amount of air in the bulb to cause a tiny difference in pressure on either side of the vanes, causing the rotor to spin.  The effect is consistent enough that this can be used as a true measure of the amount of light radiation.

Made from: beech wood, glass and steel.
Comes boxed.
Measurements: 10.8cm x 8.3cm.