A meter of radio? Far from it! A radiometer converts heat into motion. It was invented by William Crooks in 1873.
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When light hits the black side of the turbine blades, the air is heated so that the air molecules give the turbine blade a small puff and set it in motion.
You need:
- A Crooks radiometer
- A light source
Explanation:
- The radiometer consists of a small mill that is hung inside a glass bell, where the air pressure is reduced
- The turbine blades are blackened on one side, and shiny on the other side
- When light hits the black side of the turbine blades, the air is heated so that the air molecules give the turbine blade a small puff and set it in motion
- The shiny sides of the mill blades are not heated as much as the dark sides, and the pressure is lower
- Try with different light intensity, see if it affects the rotation speed. This experiment confirms that heat is molecules in motion
