EMA 3413 Part III review

EMA 3413 Part III review - EMA 3413 Part III review Ch. 10....

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EMA 3413 Part III review Ch. 10. Optical Constants Light (EM) wave o Wavelength range for visible, UV, IR o Photon energy vs. wavelength or frequency: o Propagation of light in medium Photon energy and frequency are the same as in vacuum Speed of light Wavelength Dispersion, i.e. wavelength dependence of ε , n , etc. Reflection and refraction o Snell’s law for refraction: o Total internal reflection: from high index medium to low index medium () Attenuation of light in absorptive medium o Complex dielectric constant: o Complex refractive index: ( called extinction coefficient) o , o If , then , which means material is transparent (no absorption) o Intensity of EM wave attenuates following , where the absorption coefficient and 1/ α is the characteristic penetration depth of the EM wave (or absorption length) Reflection and absorption losses in medium o Reflectance (or reflectivity): o Transmittance (or transmissivity, or transparency): o Absorptance: o 1= R + T + A if assuming no scattering losses o At normal incidence from air to a medium (or vice versa): o Multiple reflections and absorptions: example transmission of light through a mostly transparent medium Ch. 11. Atomistic Theory of the Optical Properties Atomistic (i.e., classical) theory o Motion of electrons is governed by Newton mechanics: charge particles respond to the electromagnetic field (EM optical wave) o Position of electrons is also related to polarization in the medium, from which the dielectric constant can be determined o Whenever there is absorption (), energy from the EM wave is transferred to the electron kinetic energy (motion) Drude model for free electrons o Understand what this model is
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o Without damping: Plasma frequency: ( N f is the number of free electrons per unit volume), typically in the UV range for metals (~10 15 Hz) At , , and R = 1 (100% reflection for light incident from air to the medium at normal incidence) At , , and R 0 (no reflection and no absorption, everything goes through, i.e.
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This note was uploaded on 11/16/2011 for the course EMA 3413 taught by Professor Xue during the Spring '11 term at University of Florida.

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EMA 3413 Part III review - EMA 3413 Part III review Ch. 10....

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