from __future__ import print_function, division
from visual import *

print("""
Ruth Chabay Spring 2001
A plane sinusoidal wave; show there are E and B fields throughout space.
""")

scene.width=1000
scene.height=1000
scene.x = scene.y = 0
scene.background = color.white

c = 3e8
lamb = 1e-10
h = 1e-10
omega = 2*pi*c/lamb
##line = curve(pos=[(-2*lamb,0,0), (2*lamb,0,0)])
scene.center = (-lamb,0,0)
scene.forward = (-1,-0.2,-1)

##xx = arange(-2*lamb,2.0001*lamb,lamb/20.)
xx = arange(-2*lamb,0.001*lamb, lamb/20.)

xhat = vector(1,0,0)

Evec = []
for z in [-h,0,h]:
    for y in [-h,0,h]:
        for x in xx:
            ea = arrow(pos=(x,y,z), axis=(0,lamb/10.,0), color=(1.,.6,0),
                       shaftwidth=lamb/40.)
            ba = arrow(pos=(x,y,z), axis=(0,0,0), color=(0,1,1),
                       shaftwidth=lamb/40.)
            ea.B = ba
            Evec.append(ea)

t = 0.
dt = lamb/c/100.
print('dt=',dt)
print('wavelength =', lamb)
print('omega = ', omega)
E0 = lamb/3.

while True:
    rate(50)
    t = t+dt
    for ea in Evec:
       ea.axis = (0,E0*cos(omega*t - 2*pi*ea.x/lamb),0)
       ea.B.axis = cross(xhat,ea.axis)*.7