reflection coefficient according to Fresnel equation

1 files changed, 26 insertions, 0 deletions

diff --git a/fresnel_reflection.m b/fresnel_reflection.m
new file mode 100644
index 0000000..db3b637
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+++ b/fresnel_reflection.m
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+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 index of refraction
+%% R - coefficients of reflection array [Rs, Rp]
+
+	%% see  http://en.wikipedia.org/wiki/Fresnel_equations
+	%% refracstion angle or angle of transmitted beam with respect to normal
+	sin_theta_t=n1/n2*sin(theta_i);
+
+	if ( abs(sin_theta_t) >= 1)
+		%% total internal reflection
+		R = [1, 1];
+		theta_t=sign(theta_i)*pi/2;
+		return;
+	end
+
+	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