> Measuring 3.5" in Diameter and 8.5" Tall, our Precision Radiometers are highly sensitive and will respond to just the ambient heat & light in a room. You can even cup your hands around the bulb and get the vanes to spin: our Radiometers are that sensitive to Infrared radiation (heat).
The Solar Radiometer (also known as a Light Mill) is an educational and demonstration device invented by physicist Sir William Crookes in 1873. Crookes thought it was the 'pressure' of the sunlight that made the Radiometer work. Actually, it was the infrared energy in sunlight that made the vanes turn. Inside the Radiometer there are four vanes, each has one blackened side and one silvered side. It is encased in a clear glass bulb at very low air pressure. The different colors on either side of the "vane blades" create the convection currents and that causes the blades to spin when exposed to light or heat. The more intense the light is that shines on it, the faster the vanes inside will turn. With bright light shining on it, the vanes will turn at speeds up to 3,000 RPM.
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Precision Radiometer: $49.00