# Effective Refractive Index

Can some one please explain in simple words that what is effective refractive index ?? How it is different from the refractive index ?? And how we can calculate the effective refractive index ?

Thanks.

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Here is nice explanation rp-photonics.com/effective_refractive_index.html –  freude Jun 26 '13 at 11:58
The term "effective refractive index" is also used in the theory of composite media like photonic crystals in different meaning. –  freude Jun 26 '13 at 11:59
The refractive index $n$ of a homogenous medium can be looked at as a measure of the delay which light propagating through the medium experiences, compared to the propagation of light in vacuum. For example, glass has a refractive index of about 1.3, meaning light waves propagate about 1.3 times slower in water than in vacuum. A refractive index is a property of the material itself.