def METHOD_NAME(zenith_incoming, n_2=1.3, n_1=1.):
    """  returns the coefficient t which is the ratio of the transmitted wave's
    electric field amplitude to that of the incident wave for parallel polarization (p-wave)
    this polarization corresponds to the eTheta polarization
    parallel and perpendicular refers to the signal's polarization with respect
    to the 'plane of incident' which is defindes as: "the plane of incidence
    is the plane which contains the surface normal and the propagation vector
    of the incoming radiation."
    """
    zenith_outgoing = get_fresnel_angle(zenith_incoming, n_2, n_1)
    if(zenith_outgoing is None):    #check for total internal reflection
        return 0
    t = 2 * n_1 * np.cos(zenith_incoming) / (n_1 * np.cos(zenith_outgoing) + n_2 * np.cos(zenith_incoming))
    return t