clg
clear
echo on
clc
%--------------------------- Waves.m -----------------------
%
% Propagation and Interference of Waves
%
%
%					Lecture 5
%					Chemistry 455
% 					Summer Quarter 1995
%					James B. Callis, Instructor
%
%
% Press any key to continue
pause
clc
% Now let us generate the spatial profile 
% of a traveling wave viewed at a sequence of times 
% using MATLAB.  Let us do this for the electric field 
% of electromagnetic radiation  of amplitude unity whose 
% wavelength is 500 nm. We will display the wave as amplitude 
% vs. spatial position from 0 to 950 nm in steps 
% of 50 nm.
%
%
% Press any key to continue
pause
clc
% Here are the constants:
c = 3.00e8; % Speed of light in m/sec
lam = 500e-9;% Wavelength of light, m
Dx = 50e-9; % Spatial Increment, m
L = 950e-9; % max spatial dimension, m
freq = c/lam; % frequency of light
Dt = 1/(20*freq); % Increment of time
%
% Now make up the time and space vectors:
x = 0:Dx:L; % look over 950 nm
t = 0:Dt:5/freq; % go over 5 cycles
% Press any key to continue
pause
clc
% Now calculate the mesh grid
[X,T] = meshgrid(x,t); % Always use mesh grid to synthesize 2-D
% Data
% Now calculate all of the time - space points
u = sin(2*pi*(freq*T-X/lam)); % No dot operators needed
pause
% Press any key to make a movie style plot
for i = 1:length(t)
	plot(x,u(i,:))
	title('Movie of a Traveling Sine Wave')
	xlabel('Spatial Position, m')
	ylabel('Amplitude (Arbitrary Units)')
	pause(.1)
end
% Press any key to continue
pause
clc
% Let us now consider how a wave traveling from the left
% and reflecting from the x=0 position could interfere with
% itself and cause a standing wave with stable node positions.
% Here is the wave traveling to the left:
u_left = sin(2*pi*(freq*T+X/lam)); % No dot operators needed
% Here is the wave that is reflected, inverted and traveling
% to the right:
u_right = -sin(2*pi*(freq*T-X/lam)); % No dot operators needed
% Here is the sum wave, which has stable nodes:
u_sum = u_left + u_right;
pause
% Press any key to make a movie style plot
for i = 1:length(t)
	plot(x,u_left(i,:),x,u_right(i,:),x,u_sum(i,:))
	axis([0 1e-6 -2 2])
	title('Movie of a Stationary Sine Wave')
	xlabel('Spatial Position, m')
	ylabel('Amplitude (Arbitrary Units)')
	pause(.1)
end
pause
% Press any key to see all of the sum waves on one graph
pause
clg
plot(x,u_sum)
axis([0 1e-6 -2 2])
title('Snapshots of a Stationary Sine Wave')
xlabel('Spatial Position, m')
ylabel('Amplitude (Arbitrary Units)')