It is clear that, when a light spectrum or an object enters from a vacuum to a denser medium, such as air, the velocity of that will surely decrease, and the denser the media, the greater the change in velocity and kinetic energy. It should be noted that when a photon enters a denser medium from the air, such as water or glass, the photon Impulse the media and also that media impulse the photon which causes the refraction of light. To put in another way, the impulse changes the direction of light.
According to the rotational motion of a photon, in which the component of the velocity vector are in the direction of linear motion (v ͈ ) and perpendicular to it ( v ̝ ), the change in velocity is also like that and it would not effect on its gyroradius. As a result, the R will not change so the wavelength will be constant. Thus, our changes are only in the change of the frequency ( f=v⁄λ). The important point is that the velocity of the photon depends on that media, and if the media decreases the photon velocity, the initial velocity of photons for the next medium is the last velocity in the previous medium.
Attention: If a light spectrum enters or exits a denser medium perpendicularly, refraction usually does not occur and for composite light dispersion does not occur since the angle of entry and exit of light is in one direction. But if the incidence angle of composite light is acute, the dispersion of light will usually occur and the higher the light spectrum frequencies, the greater the angle of refraction of that spectrum. Like sunlight radiation to the optical prism which causes the natural (white) light being dispersion and become colored and the higher the frequency, the greater the angle of deviation.