Force exerted by electromagnetic radiation on a body in space and directed away from the Sun or star.
a very small amount of pressure exerted on a surface by light or other electromagnetic radiation
The "push" that light gives off when it falls on something. Light coming from the Sun can push small dust particles away from the Sun.
The force exerted on the surface of a body by its absorption of light. Small particles floating in the solar system can be blown outward by the pressure of the sun-light.
The pressure (or force) on a body illuminated by electromagnetic radiation. By ordinary standards radiation pressure is extremely small. For example, the radiation pressure on an object exposed to intense sunlight is about 1011 times smaller than sea level atmospheric pressure. But for small (comparable to or smaller than the wavelengths of visible and near-visible radiation) particles subjected to only the gravitational attraction of the sun and the repulsive radiation pressure of its radiation (e.g., cometary particles), radiation pressure is not negligible, which accounts for the curvature of the tails of comets.
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the energy flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled.