S6lightrefraction

S6lightrefraction - Section 6 Optical Properties(Smith Chapter 15 skip 15.6 15.8 15 How we can use band theory(electronic structures to explain

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Section 6 Optical Properties mith Chapter 15 ip 15 6 & 15 8) (Smith Chapter 15 – skip 15.6 & 15.8) How we can use band theory (electronic structures) to y () explain colors (physical properties)? MATE 210 Refraction Diffraction
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Light and Electromagnetic Spectrum Visible light : Electromagnetic radiation with wavelength 0.400 to 700 nm ¾ Ultraviolet : 0.01 – 0.4 micrometers ¾ Infrared: 0.75 – 1000 micrometers Light has wave (EM wave) & particle (photons) nature Δ E = h ν = hc/ λ Δ E = Energy λ = wavelength ν = frequency c = 3 x10 8 m/s h = plank’s constant 6.62 x 10 -34 J s 4.136 x 10 -15 eV s MATE 210
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OPTICAL PROPERTIES OF METALS Absorption of photon by electron transition: Reflection Absorption & Emission Energy of electron unfilled states I n c i d e t p h o Δ E = h ν required! r g y ν Planck’s constant (6.63 x 10 -34 J/s) freq. of incident filled states I o f Metals have filled VB right next to empty CB light 4.13x10 -15 eV-s MATE 210 Atoms on surface absorb & re-emit visible light Adapted from Fig. 21.4(a), Callister 6e .
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OPTICAL PROPERTIES OF METALS Emission of photon by electronic transition: Reflection Energy of electron unfilled states I R “ onducting” electron Δ E conducting electron re-emitted photon from filled states material surface Reflectivity = I R /I o is between 0.90 and 0.95 • Reflected light is same frequency as incident MATE 210 Reflected light is same frequency as incident Metals appear reflective (shiny)! Adapted from Fig. 21.4(a), Callister 6e .
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OPTICAL PROPERTIES of NONMETALS Absorption by electron transition occurs if h ν > E gap Energy of electron unfilled states blue light: h ν = 3.1eV red light: h ν = 1.7eV E gap incident photon energy h ν λ c h E = filled states I o If E < 1.7eV, full absorption color is black (Si, GaAs) > 3.1eV, no absorption colorless (diamond) MATE 210 in between, partial absorption material has color!
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This note was uploaded on 09/25/2010 for the course MATE 210 taught by Professor Gary during the Spring '10 term at Aarhus Universitet.

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S6lightrefraction - Section 6 Optical Properties(Smith Chapter 15 skip 15.6 15.8 15 How we can use band theory(electronic structures to explain

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