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I have the following program that moves a wave on a string with fixed ends. The program solves the wave equation given a initial condition wave. The initial condition is a triangle wave splitting into two pulses.

Here is the code written in Python:

Here is the plot:

I want to make changes to my program so the one triangle wave pulse moves to the right and gets reflected instead of splitting up in two opposite moving pulses. How can I change my initial conditions to make this possible? I want something like this:

Here is the code written in Python:

Python:

```
from numpy import *
from matplotlib.pyplot import *
N = 201 # Number of mass points
nT = 1200 # Number of time points
mi = 0.02
m = [mi]*(N) # mass array of points on string
m[-1] = 0.02
m[0] = 0.02
ki = 10.
k = [ki]*(N) # Spring constant
k[-1] = 0
k[0] = 0
dx = 0.295
kappa = ki*dx
my = mi/dx
c = sqrt(kappa/my) # velocity
print c
dt = 0.9*dx/c # Courier
x = arange( N )*dx
t = arange( N )*dt
y = zeros( [N, nT ] )
#Initial condition with t= 0
for i in range(N-1):
if (70 <= i <= 99):
y[i,0] = (i - 69.)/30
elif (100 <= i <= 128):
y[i,0] = ((129 - i)/30.)
else:
y[i,0] = 0.
#Wave equation
for j in range(nT-1):
for i in range(N-1):
if j == 0:
y[i,j+1] = 2*y[i,j] - y[i,j] + (dt**2/m[i])*(k[i-1]*y[i+1,j] - 2*k[i-1]*y[i,j] + k[i]*y[i-1,j] )
else:
y[i,j+1] = 2*y[i,j] - y[i,j-1] + (dt**2/m[i])*( k[i-1]*y[i+1,j] - 2*k[i-1]*y[i,j] + k[i]*y[i-1,j] )
cla()
ylim(-1,1)
plot(x,y[:,j-2])
pause(0.001)
```

I want to make changes to my program so the one triangle wave pulse moves to the right and gets reflected instead of splitting up in two opposite moving pulses. How can I change my initial conditions to make this possible? I want something like this:

**EDIT:I am not sure if the pictures was correctly added!**
Last edited: