Vehicle-cpp/hkpc/software/sympy/physics/optics/tests/test_waves.py

from sympy.core.function import (Derivative, Function)
from sympy.core.numbers import (I, pi)
from sympy.core.symbol import (Symbol, symbols)
from sympy.functions.elementary.miscellaneous import sqrt
from sympy.functions.elementary.trigonometric import (atan2, cos, sin)
from sympy.simplify.simplify import simplify
from sympy.abc import epsilon, mu
from sympy.functions.elementary.exponential import exp
from sympy.physics.units import speed_of_light, m, s
from sympy.physics.optics import TWave

from sympy.testing.pytest import raises

c = speed_of_light.convert_to(m/s)

def test_twave():
    A1, phi1, A2, phi2, f = symbols('A1, phi1, A2, phi2, f')
    n = Symbol('n')  # Refractive index
    t = Symbol('t')  # Time
    x = Symbol('x')  # Spatial variable
    E = Function('E')
    w1 = TWave(A1, f, phi1)
    w2 = TWave(A2, f, phi2)
    assert w1.amplitude == A1
    assert w1.frequency == f
    assert w1.phase == phi1
    assert w1.wavelength == c/(f*n)
    assert w1.time_period == 1/f
    assert w1.angular_velocity == 2*pi*f
    assert w1.wavenumber == 2*pi*f*n/c
    assert w1.speed == c/n

    w3 = w1 + w2
    assert w3.amplitude == sqrt(A1**2 + 2*A1*A2*cos(phi1 - phi2) + A2**2)
    assert w3.frequency == f
    assert w3.phase == atan2(A1*sin(phi1) + A2*sin(phi2), A1*cos(phi1) + A2*cos(phi2))
    assert w3.wavelength == c/(f*n)
    assert w3.time_period == 1/f
    assert w3.angular_velocity == 2*pi*f
    assert w3.wavenumber == 2*pi*f*n/c
    assert w3.speed == c/n
    assert simplify(w3.rewrite(sin) - w2.rewrite(sin) - w1.rewrite(sin)) == 0
    assert w3.rewrite('pde') == epsilon*mu*Derivative(E(x, t), t, t) + Derivative(E(x, t), x, x)
    assert w3.rewrite(cos) == sqrt(A1**2 + 2*A1*A2*cos(phi1 - phi2)
        + A2**2)*cos(pi*f*n*x*s/(149896229*m) - 2*pi*f*t + atan2(A1*sin(phi1)
        + A2*sin(phi2), A1*cos(phi1) + A2*cos(phi2)))
    assert w3.rewrite(exp) == sqrt(A1**2 + 2*A1*A2*cos(phi1 - phi2)
        + A2**2)*exp(I*(-2*pi*f*t + atan2(A1*sin(phi1) + A2*sin(phi2), A1*cos(phi1)
        + A2*cos(phi2)) + pi*s*f*n*x/(149896229*m)))

    w4 = TWave(A1, None, 0, 1/f)
    assert w4.frequency == f

    w5 = w1 - w2
    assert w5.amplitude == sqrt(A1**2 - 2*A1*A2*cos(phi1 - phi2) + A2**2)
    assert w5.frequency == f
    assert w5.phase == atan2(A1*sin(phi1) - A2*sin(phi2), A1*cos(phi1) - A2*cos(phi2))
    assert w5.wavelength == c/(f*n)
    assert w5.time_period == 1/f
    assert w5.angular_velocity == 2*pi*f
    assert w5.wavenumber == 2*pi*f*n/c
    assert w5.speed == c/n
    assert simplify(w5.rewrite(sin) - w1.rewrite(sin) + w2.rewrite(sin)) == 0
    assert w5.rewrite('pde') == epsilon*mu*Derivative(E(x, t), t, t) + Derivative(E(x, t), x, x)
    assert w5.rewrite(cos) == sqrt(A1**2 - 2*A1*A2*cos(phi1 - phi2)
        + A2**2)*cos(-2*pi*f*t + atan2(A1*sin(phi1) - A2*sin(phi2), A1*cos(phi1)
        - A2*cos(phi2)) + pi*s*f*n*x/(149896229*m))
    assert w5.rewrite(exp) == sqrt(A1**2 - 2*A1*A2*cos(phi1 - phi2)
        + A2**2)*exp(I*(-2*pi*f*t + atan2(A1*sin(phi1) - A2*sin(phi2), A1*cos(phi1)
        - A2*cos(phi2)) + pi*s*f*n*x/(149896229*m)))

    w6 = 2*w1
    assert w6.amplitude == 2*A1
    assert w6.frequency == f
    assert w6.phase == phi1
    w7 = -w6
    assert w7.amplitude == -2*A1
    assert w7.frequency == f
    assert w7.phase == phi1

    raises(ValueError, lambda:TWave(A1))
    raises(ValueError, lambda:TWave(A1, f, phi1, t))