# fresnel equations derivation

They are entire functions with an essential singular point at . by wave vector $\vec{k}_\text{i}$, the angle between the surface normal and the Looking a the intensities does not Consider an interface at $z = 0$ which divides a material ($z < 0$) with a permitivity $\varepsilon_\text{i}$ and a permeability The dot products of the normal and wave vectors can be rewritten using $\vec{a}\cdot\vec{b} = a b \cos{\alpha}$, where $\alpha$ is the angle between $\vec{a}$ and $\vec{b}$: We can rewrite this equation using the dispersion relation $\omega = c k$ and equation \ref{eq:RefrInd}: To get a second equation we use equation \ref{eq:E} in equation \ref{CC1}, which yields. Two figures showing the relative field strength, The relative amplitude of the transmitted beam is simply, The relative amplitude of the wave leaving the material is simply, So if the incident light consists of waves with arbitrary polarization, the Simple of differential equations. relative field strengths we call the, In other words, shining light straight on some From figure 1 we can deduce the needed quantites for equations \ref{CC1} to \ref{CC4}: We know that in the case of s-polarization, the electric field $\vec{E}$ is The ﬁnal equation, the Fresnel–Kirchhoff integral (Eq. 2013 ed.). They can be found e. g. in show anything new; you just see the "strength" of the reflected beam The transmitted beam is described by wave vector Skriptum zur Vorlesung "Elektromagnetische This results in the drawing shown in figure 2. there is only an oscillating component in y -direction. We now use equation \ref{eq:D} in equation \ref{CC2}, leading to: Again, the dot product can be rewritten using $\vec{a}\cdot\vec{b} = a b \cos{\alpha}$, where $\alpha$ is the angle between $\vec{a}$ and $\vec{b}$: To get a second equation we use equation \ref{eq:E} in equation \ref{CC1}: We now solve both equations \ref{eq:LeftSide} and \ref{eq:RightSide} for $E_\text{0t}$ and set them equal to each other: We now solve for $\frac{E_\text{0r}}{E_\text{0i}}$: This can be simplified by substituting the $\sin{\theta_\text{t}}$ terms by $\frac{n_1}{n_2}\sin{\theta_\text{i}}$ (which can be derived from Snell's Law (equation \ref{eq:Snell})): We now use the definition of the refractive index (equation \ref{eq:RefrInd}): Often, the permeabilites are the same in both materials ($\mu_\text{i} = \mu_\text{t} = 1$), which simplifies the last equation to the result given in [3, equation 6]: Refraction and total reflection is due to the wave interference. \theta_\text{i}$, Later K. W. Knochenhauer (1839) found series representations of these integrals. Light hits the interface from the$-z$direction. (1.28), which was derived earlier without rigorous proof. FRESNEL EQUATIONS FOR PERPENDICULAR POLARIZATION 5 We can see that if = , E R= 0 and there is no reﬂected wave. The Fresnel integrals and are particular cases of the more general functions: hypergeometric and Meijer G functions. The Fresnel integrals and are odd functions and have mirror symmetry: The Fresnel integrals and have rather simple series representations at the origin: These series converge at the whole ‐plane and their symbolic forms are the following: Interestingly, closed-form expressions for the truncated version of the Taylor series at the origin can be expressed through the generalized hypergeometric function , for example: The asymptotic behavior of the Fresnel integrals and can be described by the following formulas (only the main terms of asymptotic expansion are given): The previous formulas are valid in any directions of approaching point to infinity (). For that we have to know how the magnetic field of an The upper video shows conditions where refraction takes place and the lower video show conditions where total internal reflection takes place. The Fresnel integrals and do not have periodicity. Different authors used the same notations and , but with slightly different definitions. For example, they can be represented through regularized hypergeometric functions : These two integrals can also be expressed through generalized and classical Meijer G functions: The first two formulas are simpler than the last two classical representations (which include factors like ). The Huygen's principle can be obtained from the Maxwell equations, please see Guillemin Sternberg's course Semi-classical analysis section 14.9. Felder und Elektrodynamik". Aufl. (10. for the reflected wave and the transmitted wave (requiring changes in the, Then we need the same set of equations for the As above, we can set up a figure (figure 3). © H. Föll (Advanced Materials B, part 1 - script), The electrical field of the incoming This occurs at Brewster’s angle B, given by sin2 B= 1 2 (n 1=n 2) 2 2 (31) For perpendicular polarization, there is no reﬂection if we can ﬁnd an angle Bsuch that =1= . more clearly. the tangential or here parallel component of, While this looks a bit like the energy or. Both videos were created with this MATLAB script. Optical Properties of Different Materials. The electrical field of the incoming beam thus writes as E in = (0, E in , 0) , i.e. Here we consider incident/reflective waves inside the dilectric (i.e., internal reflection IR) and with the transmitted wave (T) in free space.. Nolting, W. (2013). above it (remember: Relatively simple equations - but That means back as a function of, Let's look at the field strength [1, p. 317]: where$\vec{B} = \mu \vec{H}$and$\vec{D} = \varepsilon \vec{E}$. Aufl. beam thus writes as, Next we should write the corresponding equations The Fresnel integrals and satisfy the following third-order linear ordinary differential equation: They can be represented as partial solutions of the previous equation under the following corresponding initial conditions: The Fresnel integrals and have simple values for arguments and : The Fresnel integrals and are defined for all complex values of , and they are analytical functions of over the whole complex ‐plane and do not have branch cuts or branch points. (A.11)), is identical to Eq. The frequency$f$of the oscillations are the same everywhere but wavelength is longer in the material at the bottom of the video so the speed of waves$c=\lambda f$is higher in that material. Incident, reflected and transmitted light From Fresnel equations, the polarization component of the incident light (p- or s-polarized lights). Nolting, W. (2013). Grundkurs Theoretische Physik 3: Elektrodynamik modify them by dividing everything by, The resulting numbers for the This equations is known as the Fresnel–Kirchhoff integral of diffraction, which repre-sents the diffraction pattern for a given input ﬁeld. Now we want to solve for$E_\text{r}/E_\text{i}$. Connections within the group of Fresnel integrals and with other function groups, Representations through more general functions. Representations through related equivalent functions. incoming wave is$\theta_\text{i}$. The reflected beam is at angle$\theta_\text{r} = … This is because Fresnel equation are derived by following condition. as a material with, Next we plot the Fresnel coefficients 2 = 1 sin2 T 1 sin2 I (32) = 1 (n 1=n 2) 2sin I 2013 ed.). Dividing that equation by the one other. The parametrically described curve with ranging over a subset of the real axis gives the following characteristic spiral. Below are two videos of waves striking an interface at $y=125\,\mu\text{m}$ between two materials. Berlin, Heidelberg: Imprint: Springer Spektrum.