I'm trying to solve 1d wave equation using finite difference method. But i'm not sure that this solution is correct. Can somebody tell me what i'm doing wrong ?

clear all
close all
clc

Lx = 10;
dx = 0.1;
Nx = Lx/dx;

T = 100;
dt = 0.1;
t = 0;

a = 0.2;
C = a*dt/dx;

un = zeros(1,Nx);
un(1,[1 end])=0;
unm1 = un;
unp1 = un;

%--------------------------------------------------------------------------
n = 23;
if mod(n,2)~=0

x = linspace(0,Lx/2, n);

un0 = zeros(1,Nx);

un0([Nx/2-(n-1)/2:Nx/2+(n-1)/2])= 0.8*exp(-(2*x-Lx/2).^2);

else 
x = linspace(0,Lx/2, n);   
un0 = zeros(1,Nx);
un0([Nx/2-fix((n-1)/2):Nx/2+(n)/2])= 0.8*exp(-(2*x-Lx/2).^2*2); 
end
%--------------------------------------------------------------------------
F = figure()
while t<T  
    if t==0
    un = un0;
    end
    unm1 = un;
    un = unp1
    t = t+dt;
    for i = 2:Nx-1
        unp1(i)=2*un(i)-unm1(i)+C^2*(un(i+1)-2*un(i)+un(i-1));
        
    end

    if isvalid(F)
        
        plot(unp1,'-b')
        grid on
        ylim([-10 10])
        pause(0.005)
        
    else 
        break
    end
  
end