% Fraunhofer Diffraction Pattern
% Sinc Function and plot
% Similar to Fig. 6.4 p. 136 but now for data relating to lab.
% Steven Sahyun 140929; updated 9/30/14

clear; clf; % Clears the variables and the graph window.

screen = 50; % distance from slit to screen in cm
ymax = 4; % ± range detector moved to capture pattern
y = -ymax:0.001:ymax; 
theta = atan(y./screen); % angular range detector moved.
lambda = 650; % wavelength in nm
d = 40000; % slit width in nm 40000 nm = 0.04 mm.
k=2*pi/lambda; % Wavenumber k
x = k*d*sin(theta)/2; % variable to make reading I_theta easier.
% sinc(x) = sin(x)/x but I don't want to create a function right now.

I_0 = 1; % Maximum intensity I(0) = (E_0*d)^2 eq. 6.8
I_theta = I_0*(sin(x)./x).^2; % Equation 6.9 p. 137

plot(y,I_theta);
xlabel('distance (cm)');
ylabel('I(\theta) / I(0)');