Thursday, February 6, 2014

Angular Distribution of Diffraction Orders in Diffraction Grating

When monochromatic light falls on a diffraction grating diffraction patterns are produced on the other side of the grating. The angular distribution of the diffraction orders are given by

( a + b ) * sin(theta) = n*lambda

or, theta = asin(n*lambda / ( a + b ) )

'( a + b )' is called grating element,

'theta' is angle of diffraction,
'n' is the order of diffraction
and 'lambda' is the wavelength of light used.

To demonstrate the variation of diffraction angle with orders, a program written using OCTAVE is  presented below.

clear all
close all

ge = 2.54/15000; % ge(grating element) = (a + b)
lambda = 5893e-8; % wavelength of sodium light
n = [1 2 3];

theta = asind(n*lambda/ge);

xlabel('n'), ylabel('theta'),title('Angular Distribution of Diffraction Orders in Diffraction Grating')
grid on
axis([0 4 0 95])

The result of above program is shown on the figure.