please explain
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No, 3*10^8 m/s is the speed of electromagnetic waves in a vacuum (space).
electromagnetic waves slow significantly in other mediums. For example, the speed of electromagnetic waves in lead is about 116,230,400 meters/second.
electromagnetic waves slow significantly in other mediums. For example, the speed of electromagnetic waves in lead is about 116,230,400 meters/second.
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It varies with the medium, albeit slightly.
First, the medium shouldn't be conducting. It can be a dielectric medium whose magnetic and electric (propagation) parameters are the relative permeability 'mu', |u` and relative permittivity, 'epsilon' e` such that the retarding factor is
1/√[|u` e`].
The speed of light 3*10^8 m/s must be multiplied with this factor to get the speed of light in that medium. In practice |u` is al most 1 and so the speed gets retarded by a factor
1/√e`
which is the same as 'refractive index' (normally we come across in connection with light propagating through glass).
First, the medium shouldn't be conducting. It can be a dielectric medium whose magnetic and electric (propagation) parameters are the relative permeability 'mu', |u` and relative permittivity, 'epsilon' e` such that the retarding factor is
1/√[|u` e`].
The speed of light 3*10^8 m/s must be multiplied with this factor to get the speed of light in that medium. In practice |u` is al most 1 and so the speed gets retarded by a factor
1/√e`
which is the same as 'refractive index' (normally we come across in connection with light propagating through glass).