49 lines
2.1 KiB
Python
49 lines
2.1 KiB
Python
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from sympy.functions.elementary.miscellaneous import sqrt
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from sympy.physics.optics import Medium
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from sympy.abc import epsilon, mu, n
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from sympy.physics.units import speed_of_light, u0, e0, m, kg, s, A
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from sympy.testing.pytest import raises
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c = speed_of_light.convert_to(m/s)
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e0 = e0.convert_to(A**2*s**4/(kg*m**3))
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u0 = u0.convert_to(m*kg/(A**2*s**2))
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def test_medium():
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m1 = Medium('m1')
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assert m1.intrinsic_impedance == sqrt(u0/e0)
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assert m1.speed == 1/sqrt(e0*u0)
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assert m1.refractive_index == c*sqrt(e0*u0)
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assert m1.permittivity == e0
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assert m1.permeability == u0
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m2 = Medium('m2', epsilon, mu)
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assert m2.intrinsic_impedance == sqrt(mu/epsilon)
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assert m2.speed == 1/sqrt(epsilon*mu)
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assert m2.refractive_index == c*sqrt(epsilon*mu)
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assert m2.permittivity == epsilon
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assert m2.permeability == mu
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# Increasing electric permittivity and magnetic permeability
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# by small amount from its value in vacuum.
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m3 = Medium('m3', 9.0*10**(-12)*s**4*A**2/(m**3*kg), 1.45*10**(-6)*kg*m/(A**2*s**2))
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assert m3.refractive_index > m1.refractive_index
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assert m3 != m1
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# Decreasing electric permittivity and magnetic permeability
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# by small amount from its value in vacuum.
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m4 = Medium('m4', 7.0*10**(-12)*s**4*A**2/(m**3*kg), 1.15*10**(-6)*kg*m/(A**2*s**2))
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assert m4.refractive_index < m1.refractive_index
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m5 = Medium('m5', permittivity=710*10**(-12)*s**4*A**2/(m**3*kg), n=1.33)
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assert abs(m5.intrinsic_impedance - 6.24845417765552*kg*m**2/(A**2*s**3)) \
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< 1e-12*kg*m**2/(A**2*s**3)
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assert abs(m5.speed - 225407863.157895*m/s) < 1e-6*m/s
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assert abs(m5.refractive_index - 1.33000000000000) < 1e-12
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assert abs(m5.permittivity - 7.1e-10*A**2*s**4/(kg*m**3)) \
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< 1e-20*A**2*s**4/(kg*m**3)
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assert abs(m5.permeability - 2.77206575232851e-8*kg*m/(A**2*s**2)) \
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< 1e-20*kg*m/(A**2*s**2)
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m6 = Medium('m6', None, mu, n)
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assert m6.permittivity == n**2/(c**2*mu)
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# test for equality of refractive indices
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assert Medium('m7').refractive_index == Medium('m8', e0, u0).refractive_index
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raises(ValueError, lambda:Medium('m9', e0, u0, 2))
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