Optical Properties of Materials: Light, Reflection, Refraction, and Color, Study notes of Materials science

Download Optical Properties of Materials: Light, Reflection, Refraction, and Color and more Study notes Materials science in PDF only on Docsity! Materials 100A, Class 14, Optical Properties Ram Seshadri MRL 2031, x6129 seshadri@mrl.ucsb.edu; http://www.mrl.ucsb.edu/∼seshadri/teach.html Light Some basics: Electromagnetic radiation has electric and magnetic field components that are perpendicular to each other and to the direction of propagation. The propagation velocity is c, and this is constant for all electromagnetic radiation in vacuum: c ∼ 3× 108 m/s. c is related to the vacuum permittivity 0 and the vacuum permeability µ0 in the following manner: c = 1 √ 0µ0 c is equal to the product of the frequency and the wavelength: c = νλ The energy of any light photon is proportional to the frequency of the photon so: E = hν where ν is in Hz (s−1) and h is the Planck constant h = 6.63× 10−34 Js. It is also possible then to write: E = hc λ Electromagnetic radiation with different frequencies have correspondingly, different energies and wavelengths. Visible electromagnetic radiation (“light”) has wavelengths ranging from 400 to 700 nm. Light and metals — reflection: Since metals have free electrons, all energies are absorbed and re-emitted. Hence the reflectivity. Yellow/red metals such as Cu and Au are so colored because they absorb a little in the blue. Refraction: The refractive index n of a material is the ratio of the velocity of light in vacuum (always c) to the velocity of light in that material v: n = c v If the material has a dielectric constant  and permeability ν, then v = 1 √ µ 1