def test_add_value(self):
"""Values are added not replaced"""
fp1 = FieldPoint(0, 0, 0)
fp1.add(1 + 2j)
self.assertEqual(fp1.real(), 1)
self.assertEqual(fp1.imag(), 2)
self.assertEqual(fp1.abs(), (1**2 + 2 * 2)**0.5)
self.assertEqual(fp1.phase(), math.atan(2))
fp1.add(2 + 2j)
self.assertEqual(fp1.real(), 3)
self.assertEqual(fp1.imag(), 4)
self.assertEqual(fp1.abs(), (3**2 + 4**2)**0.5)
self.assertEqual(fp1.phase(), math.atan(4. / 3.))
def test_decay_rate(self):
""" check amplitude decays at rate 1/r"""
s = SourcePoint(0, 0, 0, 1, 0)
f = FieldPoint(1, 0, 0)
frequency = 1
wavelength = speed_of_light / frequency
k = 2 * pi / wavelength
propagate_single(s, f, k)
self.assertEqual(round(f.real(), 6), 0.079577)
self.assertEqual(round(f.imag() / 1e-9, 6), 1.66782)
f2 = FieldPoint(2, 0, 0)
propagate_single(s, f2, k)
self.assertEqual(f.abs() / f2.abs(), 2)
f4 = FieldPoint(4, 0, 0)
propagate_single(s, f4, k)
self.assertEqual(round(f.abs() / f4.abs(), 6), 4)