def calc_lum_ratio_from_radii_teff_ratios(radii_ratio, teff_ratio):
    """Calculate ratio of the luminosities of the smaller star to greater star
    from the ratios of their radii and effective temperature.
    
    Parameters
    ----------
    radii_ratio : float
        Ratio of radii of smaller-sized star to greater-sized star.
        radii_ratio = radius_s / radius_g
    teff_ratio : float
        Ratio of effective temperatures of smaller-sized star to greater-sized star.
        teff_ratio = teff_s / teff_g
        
    Returns
    -------
    lum_ratio : float
        Ratio of luminosities of smaller-sized star to greater-sized star.
        lum_ratio = lum_s / lum_g

    Notes
    -----
    lum_ratio = lum_s / lum_g
              = (4 * pi * radius_s**2 * sigma * teff_s**4) / (4 * pi * radius_g**2 * sigma * teff_g**4)
    radii_ratio = radius_s / radius_g
    teff_ratio = teff_s / teff_g
    => lum_ratio = radii_ratio**2 * teff_ratio**4
    From equation 3.17 in section 3.4 of [1]_
    
    References
    ----------
    .. [1] Carroll and Ostlie, 2007, An Introduction to Modern Astrophysics
    
    """
    lum_ratio = radii_ratio ** 2.0 * teff_ratio ** 4.0
    return lum_ratio
