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Laser cooling is a method of cooling materials very close to absolute zero by converting some of material's motional energy into light. Kinetic energy and thermal energy of the material are synonyms here, because they represent the energy associated with Brownian motion of the material. Atoms traveling towards a laser light source perceive a ...
Intensity can be found by taking the energy density (energy per unit volume) at a point in space and multiplying it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area (i.e., surface power density). The intensity of a wave is proportional to the square of its amplitude.
A point source of light produces spherical wavefronts. The irradiance in this case varies inversely with the square of the distance from the source. = =, where r is the distance; P is the radiant flux; A is the surface area of a sphere of radius r.
The force of attraction or repulsion between two electrically charged particles, in addition to being directly proportional to the product of the electric charges, is inversely proportional to the square of the distance between them; this is known as Coulomb's law. The deviation of the exponent from 2 is less than one part in 10 15. [8]
The component of the photophoretic force responsible for this phenomenon is called the radiometric force. [13] This comes as a result of uneven distribution of radiant energy (source function within a particle). Indirect photophoretic force depends on the physical properties of the particle and the surrounding medium.
Light, or more generally an electromagnetic wave, carries not only energy but also momentum, which is a characteristic property of all objects in translational motion. The existence of this momentum becomes apparent in the "radiation pressure " phenomenon, in which a light beam transfers its momentum to an absorbing or scattering object, generating a mechanical pressure on it in the process.
There are two factors that determine the degree to which a medium containing particles will attenuate a light beam: the number of particles encountered by the light beam, and the degree to which each particle extinguishes the light. [15] Assume that a beam of light enters a material sample. Define z as an axis parallel to the direction of the ...
The optical force is a phenomenon whereby beams of light can attract and repel each other. The force acts along an axis which is perpendicular to the light beams. Because of this, parallel beams can be induced to converge or diverge. The optical force works on a microscopic scale, and cannot currently be detected at larger scales.