>>11809069>Is there a layman's explanation for why the refractive index of a material squared is the same as it's dielectric constant?> I understand the equations but my mind just goes blank if I try to think about it logically.I'll add something to
>>11809118 's cool explanation
Maxwell's equation basically say that a variation in time of the electric field creates a Magnetic field and vice versa. A wave propagates because a variation in time of the electric field will create a variation in time of the magnetic field over and over again.
Maxwell's equation are the equation that describe the behavior or EM (Electro-Magnetic) waves in space in which two constants (permittivity epsilon and permeability mu) appear (pic related). If you take the inverse of the product of these constants, you get the speed of light squared.
But these constants happen to change when an EM wave propagates through a medium that is not free space. If the permittivity is 4 times as high as in vacuum and permeability doesn't change , if you take the relationship above, that means the speed of light will be twice as slow.
The ratio of permittivity/permeability in a medium over the permittivity/permeability in vacuum is called the relative permittivity (respectively permeability).
In order to intuitively display the speed of light within a certain medium, physicists created the refractive index as the square root of the product of the relative permittivity and relative permeability
dielectric refractive index is in the case where the relative permeability is 1 (as dielectric medias have a relative permeability of 1). The refractive index therefore simplife to the square root of permittivity.
