As shown, two Silicon (Si) abrupt p-n unction diodes are fabricated with uniform donor doping concentrations of  and in the n-regions of the diodes, and uniform acceptor doping concentrations of  in the p-regions of the diodes, respectively. Assuming that the reverse bias voltage is built-in potentials of the diodes, the ratio  of their reverse bias capacitances for the same applied reverse bias, is _________ .