Wednesday, December 8, 2010

Photon generates upthrust


I think this is a very funny work [Nature Photon. doi:10.1038/nphoton.2010.266 (2010)], which demonstrates that photons carry energy and momentum, just as other forms of matter. This working mechanism is quite straightforward, much the way as air supports air crafts.
Grover Swartzlander at the Rochester Institute of Technology in New York and his colleagues shone a weakly focused laser beam through the roughly semi-cylindrical rods, which refracted the light rays. This refraction changed the direction of the rays' momentum, causing an equal and opposite momentum change on the rods themselves. Because of the rods' asymmetrical shape, the momentum shift was directed more towards one side, driving the rods upwards at around 2.5 micrometres per second.
[Nature, 468:734]

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