Sinusoidal wave.py

from vpython import *

scene.width = 1000
scene.height = 600
scene.background = color.black

#Parameters
wavelength = 600
scene.range = 1*wavelength
E0 = 1e4
c = 3e8

frequency = c/wavelength
period = 1/frequency
dt = 3e-4*period
t = 0
pointlist=arange(-3*wavelength/2, 3*wavelength/2, wavelength/16)
arrowlist=[]

# Loop over observation locations and create electric and magnetic field arrows there
for x in pointlist:
    Earrow=arrow(pos=vector(x,0,0), color=color.orange, shaftwidth=wavelength/40)
    Earrow.B=arrow(pos=vector(x,0,0), color=color.cyan, shaftwidth=wavelength/40)
    arrowlist.append(Earrow)
    if abs(x) < 0.03*wavelength:
        Earrow.color = color.red
        Earrow.B.color = color.black

yy = -wavelength*.65
xx = -0.5*wavelength
dyy = wavelength/5
pts = [vector(xx, yy+dyy, 0), vector(xx, yy-dyy, 0),vector(xx, yy, 0),vector(xx+wavelength, yy, 0),
       vector(xx+wavelength, yy+dyy, 0), vector(xx+wavelength, yy-dyy, 0)]
ruler = curve(color=color.green, pos=pts, radius=wavelength/60)
run = True

def B_Runbutton(b):
    global run
    run = not run
    if run:
        b.text = "Pause"
    else:
        b.text = "Run"

button(text="Pause", bind=B_Runbutton)

scene.append_to_caption("      The green marker indicates the length of one wavelength.")
#Dynamics of wave motion
while True:
    rate(1000)
    if not run: continue
    for Earrow in arrowlist:
        E = vector(0,E0*cos(2*pi*(frequency*t-Earrow.pos.x/wavelength)),0)
        B = vector(0,0,E.y/c)
        Earrow.axis = E/40
        Earrow.B.axis = B*(c/50)
    t = t+dt