%% Listing 4.1 (ch4ex1.m)
clear; close all;
% set s to zero so that 1/n^2 can be repeatedly added to it
s=0;
N=10000; % set the upper limit of the sum
for n=1:N % start of the loop
    s = s + 1/n^2; % add 1/n^2 to s each iteration
end % end of the loop
fprintf(' Sum = %g \n',s) % print the answer



%% Listing 4.4 (ch4ex4.m)
clear; close all;
a=1;
b=3;
if a>0
    c=1 %Ifaispositivesetcto1
else
    c=0  %if a is 0 or negative, set c to zero
end


%% 
% if either a or b is non-negative, add them to obtain c;
% otherwise multiply a and b to obtain c

if a>=0 | b>=0  % either non-negative
c=a+b
else
   c=a*b  % otherwise multiply them to obtain c
end

%% Listing 4.5 (ch4ex5.m)
clear; close all;
term=1  % load the first term in the sum, 1/1^2=1
s=term;  % load s with this first term

% start of the loop - set a counter n to one
n=1;
while term > 0.001  % loop until term drops below 1e-10
   n=n+1; % add 1 to n so that it will count: 2,3,4,5,...
   term=1/n^2; % calculate the next term to add
   s=s+term;  % add 1/n^2 to s until the condition is met
end  % end of the loop
fprintf(' Sum = %g \n',s)

%% Listing 4.6 (ch4ex6.m)
clear; close all;
term=1;  % load the first term in the sum, 1/1^2=1
s=term;  % load s with this first term
% start of the loop - set a counter n to one
n=1;
while term > 1e-100  % set a ridiculously small term.
                     % Don't really do this, as you
                     % only have 15 digits of precision.
   n=n+1; % add 1 to n so that it will count: 2,3,4,5,...
   term=1/n^2;
   s=s+term;
   if n>1000
       break
   end
   
end  % end of the loop
fprintf(' Sum = %g \n',s)


%% Listing 7.4 (SquareWell.m)
%function [x,psi,E] = SquareWell(n,a,NPoints)
% Calculate the energy and wavefunction for an
% electron in an infinite square well
%
% Inputs: n is the energy level; must be a positive integer
%         a is the well width in nanometers
%         NPoints is the number of points in the x grid
%
% Outputs: x is the grid for the plot, measured in nanometers
%          psi is the normalized wave function
%          E is the energy of the state in electron-volts
% Make the x-grid
xmin = 0;
xmax = a;
x = linspace(xmin,xmax,NPoints);
% Wave number for this energy level
k = n * pi / a;
% Calculate the wave function
psi = sqrt(2/a) * sin(k*x);
global hbar m
% Calculate energy in electron-volts
E = n^2*pi^2*hbar^2 / (2*m*(a*1e-9)^2) / 1.6e-19;
end

%% Listing 7.5 (ch7ex5.m)
clear; close all;
global hbar m
% Constants in MKS units
hbar = 1.05e-34;
m=9.11e-31;
% remember that n must be a positive integer
n=3;
% Set the width to an Angstrom
a=0.1;
% Get the values
[x,psi,Energy] = SquareWell(n,a,100);
% Make the plot and label it
plot(x,psi)
s=sprintf('\\Psi_%g(x); a=%g nm; Energy=%g eV',n,a,Energy);
title(s);
xlabel('x (nm)');
ylabel('\Psi(x)');