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Does the amplitude of the light ray decrease when it moves from a rarer to a denser medium?

I think that since amplitude depends upon the energy of the light ray, it should decrease. This is because of the kinetic energy of the light wave decreases (velocity decreases as light travels from rarer to denser medium), hence the energy of the wave falls.

This explanation does not seem convincing, could anyone provide some insights?

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  • $\begingroup$ duplicate of several questions $\endgroup$ Sep 29, 2015 at 17:54
  • $\begingroup$ Could you please provide me with a link that will lead me to that answer? $\endgroup$
    – Student
    Sep 30, 2015 at 5:23
  • $\begingroup$ Maybe physics.stackexchange.com/q/22385 or physics.stackexchange.com/q/21336 . The point is that $ E = h\nu $ and frequency does not change. $\endgroup$ Sep 30, 2015 at 11:25
  • $\begingroup$ But then you are treating light as a particle whereas refraction is a wave phenomena. $\endgroup$
    – Student
    Oct 1, 2015 at 10:58

2 Answers 2

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Fresnel's equations sum up the behaviour of light across medium boundaries in terms of linear dielectric response. This problem was solved in the 19th century.

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The amplitude of the electric field in the medium depends on the medium's permittivity, which is not directly related to its density.

Kinetic energy of the light wave decreases(velocity decreases as light travels from rarer to denser medium), hence the energy of the wave falls.

This is not true -- the energy in an electromagnetic wave does not depend on its velocity. Additionally, the speed depends on the permittivity and permeability, not the density.

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  • $\begingroup$ Is the same true for sound? $\endgroup$
    – Student
    Oct 1, 2015 at 15:33

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