Change in speed and wavelength of light while travelling from one med

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Light changes speed and wavelength when transitioning between media due to the interaction with atoms in the medium. While light travels at speed 'c' in a vacuum, its effective speed decreases in materials like glass due to the time lag in absorption and re-emission by atoms. This process involves excitation and de-excitation of particles, where emitted light can scatter in various directions. Despite the potential for reduced intensity in the direction of propagation, significant intensity is still observed, indicating that absorption does not fully account for the change in speed. Understanding these mechanisms reveals the complexities of light behavior in different optical environments.
shantanuphadke
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what is the mechanism by which light changes its speed and wavelength while traveling from one medium to other. I know it is c/n or lamda/n and know it comes from maxwells equations, but what is the physical reason behind this?
 
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Well, if you take one of the two : velocity or wavelength to be changing, change in the other will follow.
For the physical reason behind it, if I'm not wrong, I believe it is the average or effective speed of light that changes in a different optical medium; and between atoms, light still travels at 'c'. If you buy this argument, then to explain the change in velocity of light isn't so hard. The extra time light takes to cover the same distance in say, glass as in vacuum can be attributed to the time lag between the absorption and release of the photon of light by the medium's atoms. And there may be still a lot more going on inside than this.
 
but when particle absorbs light, it gets excited and in the process of de-excitation it emmits light.But that emmited light can follow any direction except the direction in which photon got excited.so we could expect intensity to decrease a lot but it is not observed ( appreciable intesity observed in the direction of propagation).Then how could absorption take place?
 
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