Instructor: Lichuan Gui lichuan-gui@uiowa

Measurements in Fluid Mechanics058:180 (ME:5180)Time & Location: 2:30P - 3:20P MWF 3315 SCOffice Hours: 4:00P – 5:00P MWF 223B-5 HL Instructor: Lichuan Gui lichuan-gui@uiowa.edu Phone: 319-384-0594 (Lab), 319-400-5985 (Cell) http://lcgui.net

Lecture 7. Optical experimentation: Nature of light

Background for optical experimentation Light ( classical Electromagnetic theory ) - radiation that propagates through vacuum in free space, - in the form of electromagnetic waves, - both oscillating transversely to the propagation direction - and normal to each other. - intensities of the electric and magnetic fields oscillate harmonically in time t and along propagation direction x.  - wavelength T – periodof oscillation - frequency of oscillation:  =1/T - wave number: =1/ - phase speed:  = /T =  - speed of light propagation in vacuum: c = 2.998  108  300,000 km/s - relation between amplitudes of electric and magnetic fields:

Background for optical experimentation Wave front - a surface with constant phase in electric/magnetic filed. - plane wave: all wave fronts are plane - spherical wave - cylindrical wave

Background for optical experimentation Polarization - associated with the orientation of the plane of oscillation of the electric field. - circularly polarized - plane/linear polarized - elliptically polarized - randomly polarized (unpolarized)

Background for optical experimentation The colors of light Visible light: wavelength range 380-750 nm Visible light colors Different types of radiation Refractive index c – light speed in vacuum v – light speed in medium

Background for optical experimentation e – charge of an electron me – mass of an electron L – Loschmidt’s number m – molecular weight  – frequency of visualizing light i– resonant frequency of distorted electron fi– oscillator strength of distorted electron Relationship between refractive index and density Lorentz-Lorenz (or Clausius-Mosotti) express: Gladstone-Dale formula - Simplified for gases n – refractive index K – Gladstone-Dale constant  – density Dependency of refractive index of water on temperature Tc (20-34C) for =632.8 nm: In gas mixture of N components:

Background for optical experimentation Light refraction Law of refraction Application of refraction: convergent and divergent glass lenses

Background for optical experimentation Light reflection Law of reflection Critical angle Total internal reflection - glass-air interface: c=42 - glass-waster interface: c=62

Background for optical experimentation Light absorption I0 – radiant intensity of incident light I – radiant intensity of passing light l – length of path – absorption (attenuation) coefficient - extremely large for opaque material - defined at which I=37%I0 - small for transparent material Beer’s law: Penetration Depth: - a measure of how deep light can penetrate into a material. Birefringence (double refraction) decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. - unequal indices of refraction in two directions

Homework - Read textbook 5.1-5.2 on page 98-107 • Questions and Problems: 1 and 2 on page 142 - Due on 09/10

Start to write a Matlab program • Determine location of maximal gray value i – number of lines j – number of columns image01.bmp A(i,j) for i=1,2,3, M; j=i=1,2,3, N 42 31 38 47 40 28 21 30 36 54 47 47 32 31 41 27 30 30 36 25 31 25 28 44 60 49 45 51 44 49 37 45 50 35 54 47 57 41 39 40 44 52 38 52 50 22 23 48 48 43 49 50 42 40 33 47 36 29 40 50 47 26 26 54 56 38 45 42 32 46 40 38 62 48 38 40 51 36 48 58 47 40 48 48 43 43 51 43 30 35 39 34 34 50 36 51 49 38 44 50 52 59 56 46 51 32 43 43 43 45 21 33 35 41 45 33 43 41 52 49 46 37 37 37 49 36 39 50 42 42 44 26 12 25 26 30 47 41 33 53 53 40 50 59 40 33 41 45 39 37 36 29 28 35 44 32 26 44 34 38 35 24 67 53 50 46 49 23 33 46 47 39 36 63 36 33 25 34 55 44 38 28 28 28 30 43 39 27 39 44 39 39 58 37 34 34 48 37 15 38 36 35 36 51 36 60 38 35 40 47 35 53 53 27 30 48 33 47 34 38 35 37 30 40 41 36 50 34 33 53 39 30 34 46 53 52 41 43 41 44 54 41 53 44 34 39 16 24 32 53 50 30 29 57 33 36 56 48 44 56 33 34 37 46 45 54 41 30 24 14 29 39 40 39 46 51 36 39 35 31 51 47 56 57 54 43 50 32 54 46 27 32 28 34 27 34 42 40 39 47 44 36 33 61 30 47 48 59 45 46 38 53 52 28 32 41 52 29 36 36 35 45 36 39 35 22 36 21 24 50 46 54 41 37 27 27 31 23 33 31 33 21 26 34 28 43 40 32 42 50 27 32 44 54 51 60 58 43 31 43 48 40 61 39 36 32 41 35 44 33 50 44 29 37 35 33 55 56 75 85 60 39 40 52 33 50 39 36 23 37 12 21 22 23 55 41 26 27 26 49 68 103 255 167 73 36 12 12 30 28 46 37 19 29 28 30 27 48 43 43 29 40 51 57 84 184 149 63 29 20 5 28 31 47 46 28 35 26 37 35 46 26 37 35 32 39 41 47 59 50 54 48 31 22 21 30 38 37 37 48 20 38 35 33 37 23 27 44 48 59 37 44 42 47 50 36 41 24 37 28 48 35 41 22 50 47 51 32 38 28 41 45 48 55 42 34 38 27 42 22 31 19 24 46 38 44 39 55 44 56 38 40 40 31 33 34 36 32 25 39 19 19 25 27 14 10 54 34 22 43 50 54 52 36 38 21 34 18 46 46 44 52 38 24 30 23 32 45 15 26 48 38 44 32 49 46 47 37 29 47 40 21 47 36 40 38 26 27 31 34 37 35 24 36 31 43 MatlabProgram.m Clear; A=imread('image01.bmp'); [M N]=size(A);Imax=0; Jmax=0; Gmax=0; for i=1:M for j=1:N if A(i,j)>Gmax Gmax=A(i,j); Imax=i; Jmax=j; end end end [Imax JmaxGmax] >> MatlabProgram ans= 17 11 255 12

Instructor: Lichuan Gui lichuan-gui@uiowa