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The phase shift of the reflected wave on total internal reflection can similarly be obtained from the phase angles of r p and r s (whose magnitudes are unity in this case). These phase shifts are different for s and p waves, which is the well-known principle by which total internal reflection is used to effect polarization transformations .
By Fresnel's sine law, r s is positive for all angles of incidence with a transmitted ray (since θ t > θ i for dense-to-rare incidence), giving a phase shift δ s of zero. But, by his tangent law, r p is negative for small angles (that is, near normal incidence), and changes sign at Brewster's angle, where θ i and θ t are complementary.
Thus the phase shift δ p is 180° for small θ i but switches to 0° at Brewster's angle. Combining the complementarity with Snell's law yields θ i = arctan (1/n) as Brewster's angle for dense-to-rare incidence. [Note 15] (Equations and are known as Fresnel's sine law and Fresnel's tangent law. [40]
Since there are two equations relating and to and , these two representations are equivalent. In the new representation, propagation over a distance L {\displaystyle L\,} into the positive direction of z {\displaystyle z\,} is described by the matrix belonging to the special linear group SL( 2 , C )
The sector contour used to calculate the limits of the Fresnel integrals. This can be derived with any one of several methods. One of them [5] uses a contour integral of the function around the boundary of the sector-shaped region in the complex plane formed by the positive x-axis, the bisector of the first quadrant y = x with x ≥ 0, and a circular arc of radius R centered at the origin.
where and are the angles of incidence and refraction; these equations are known respectively as Fresnel's sine law and Fresnel's tangent law. [197] By allowing the coefficients to be complex, Fresnel even accounted for the different phase shifts of the s and p components due to total internal reflection. [198]
Kirchhoff's integral theorem, sometimes referred to as the Fresnel–Kirchhoff integral theorem, [3] uses Green's second identity to derive the solution of the homogeneous scalar wave equation at an arbitrary spatial position P in terms of the solution of the wave equation and its first order derivative at all points on an arbitrary closed surface as the boundary of some volume including P.
Thus, whatever phase is associated with reflection on one side of the interface, it is 180 degrees different on the other side of the interface. For example, if r has a phase of 0, r’ has a phase of 180 degrees. Explicit values for the transmission and reflection coefficients are provided by the Fresnel equations