A radiometer consists of a set of vanes, each shiny on one side and blackened on the other, that are mounted in an evacuated vessel. When exposed to light, the vanes spin. The blackened vanes retreat from the light source. The black surface is warmer than the shiny surface and gas molecules will recoil faster from the hot surface. The slight difference in molecule recoil is what causes the device to spin.
Light has qualities of both waves and particles.
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