How do dispersion forces occur?

Answer 1

Dispersion is due to refraction.

In optics, dispersion is a phenomenon that causes the separation of a wave into spectral components with different wavelengths, due to a dependence of the wave's speed on its wavelength. It is most often described in light waves, but it may happen to any kind of wave that interacts with a medium or can be confined to a waveguide, such as sound waves. Dispersion is sometimes called chromatic dispersion to emphasize its wavelength-dependent nature.

There are generally two sources of dispersion: material dispersion, which comes from a frequency-dependent response of a material to waves; and waveguide dispersion, which occurs when the speed of a wave in a waveguide depends on its frequency. The transverse modes for waves confined laterally within a finite waveguide generally have different speeds (and field patterns) depending upon the frequency (that is, on the relative size of the wave, the wavelength, compared the size of the waveguide).

Dispersion in a waveguide used for telecommunication results in signal degradation, because the varying delay in arrival time between different components of a signal "smears out" the signal in time. A similar phenomenon is modal dispersion, caused by a waveguide having multiple modes at a given frequency, each with a different speed. A special case of this is polarization mode dispersion (PMD), which comes from a superposition of two modes that travel at different speeds due to random imperfections that break the symmetry of the waveguide.

Answer 2

Motion of electrons
motion of electrons

Answer 3

Dispersion forces are formed when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes referred to as an induced dipole.