move code to directory with speaking name

1 files changed, 28 insertions, 0 deletions

diff --git a/beam_tracing/fresnel_reflection.m b/beam_tracing/fresnel_reflection.m
new file mode 100644
index 0000000..347d60b
--- /dev/null
+++ b/beam_tracing/fresnel_reflection.m
@@ -0,0 +1,28 @@
+function [R, theta_t] = fresnel_reflection(n1, n2, theta_i)
+%% calculates intensity  reflection coefficient for s and p polarizations
+%% for light travelling from material with index of refraction n1 to material with n2
+%% theta_i - incident angle in medium 1 with respect to normal, could be a vector
+%% R - coefficients of reflection array [Rs, Rp]
+%% theta_t - transmitted/refracted angle in medium 2 with respect to normal
+
+	if ( size(theta_i)(1) != 1) 
+		error('theta_i must be a vector or scalar');
+	end
+
+	%% see  http://en.wikipedia.org/wiki/Fresnel_equations
+	%% refraction angle or angle of transmitted beam with respect to normal
+	sin_theta_t=n1/n2*sin(theta_i);
+	%% special cases: total internal reflection
+	indx = (abs(sin_theta_t) >= 1);
+	sin_theta_t( indx ) = sign( sin_theta_t(indx) );
+
+
+	theta_t = asin(sin_theta_t); % angle of refraction or transmitted beam
+
+	cos_theta_t = cos( theta_t );
+	cos_theta_i = cos( theta_i );
+
+	Rs = ( ( n1*cos_theta_i - n2*cos_theta_t ) ./ ( n1*cos_theta_i + n2*cos_theta_t ) ).^2;
+	Rp = ( ( n1*cos_theta_t - n2*cos_theta_i ) ./ ( n1*cos_theta_t + n2*cos_theta_i ) ).^2;
+	R = [Rs; Rp];
+end