However, the electrons have inertia - they cannot respond instantly to the incoming field, so there is a time-lag between the incoming and outgoing electromagnetic oscillations. This time-lag (or phase difference for the technically minded) is encoded in the complex refractive index. read more
Because if it didn’t quack, it wouldn’t be a duck. Well, if a material doesn’t have a complex index of refraction, then it can’t be a metal. The complex index of refraction comes because metals have free charge carriers (actually electrons) that can oscillate in response to an incoming electromagnetic field (i.e. when you shine light on it). read more
When a light wave of the form E=E 0 e iω hits the surface of a metal, the refractive index if given(considering restoring force of metal atoms and damping equal to 0), by n 2 =1-p 2 /ω 2 where p=plasma frequency and ω= frequency of the wave. In the case where n 2 <0, n is complex. and hence the light wave is completely damped. read more
index n= n0+ in00for silver, aluminum, gold, copper, chromium, nickel, tungsten, titanium, beryl- lium, palladium, and platinum using either the Drude (Equation 3), Lorentz-Drude (Equation 4), or Brendel-Bormann (Equation 5 models in the range 200nm to 2000nm. read more