'Returns wavelength of the wave.
It depends on the medium of the wave.
Examples
>>> from sympy import symbols
>>> from sympy.physics.optics import TWave
>>> A, phi, f = symbols(\'A, phi, f\')
>>> w = TWave(A, f, phi)
>>> w.wavelength
299792458*meter/(second*f*n)'

@property
def wavelength(self):

    return (c / (self._frequency * self._n))
