Optical “Bernoulli” Forces

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Light scattering from a rotating dielectric cylinder

Light scattering from a rotating dielectric cylinder

Ramis Movassagh and Steven G. Johnson
By Bernoulli’s law, an increase in the relative speed of a fluid around a body is accompanies by a decrease in the pressure.
Therefore, a rotating body in a fluid stream experiences a force perpendicular to the motion of the fluid because of the unequal relative speed of the fluid across its surface. It is well known that light has a constant speed irrespective of the relative motion.
Does a rotating body immersed in a stream of photons experience a Bernoulli-like force?
We show that, indeed, a rotating dielectric cylinder experiences such a lateral force from an electromagnetic wave.
In fact, the sign of the lateral force is the same as that of the fluid-mechanical analogue as long as the electric susceptibility is positive (ε>ε0), but for negative-susceptibility materials (e.g. metals) we show that the lateral force is in the opposite direction.
Because these results are derived from a classical electromagnetic scattering problem, Mie-resonance enhancements that occur in other scattering phenomena also enhance the lateral force.

Reab also: Optical Bernoulli Forces Could Steer Objects Bathed in Light, Say Theorists

Written by physicsgg

September 19, 2013 at 5:01 pm

Posted in Fluid Dynamics

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