radiation pressure

noun Physics.

1. the pressure exerted on a surface by electromagnetic radiation or by sound waves.

1. Force per unit area exerted by waves or particles of radiation, especially photons. Though photons have no mass, they do have momentum, and can transfer that momentum to other particles upon impact. The amount of pressure exerted by a given amount of radiation depends on whether the radiation is absorbed or reflected. Radiation pressure is responsible for the Casimir effect; solar radiation pressure is exploited in the design of solar sails.