The magnitudes of power of a biconvex lens (refractive index \( 1.5 \)) and that of a plano-concave lens (refractive index \( = 1.7 \)) are same. If the curvature of plano-concave lens exactly matches with the curvature of back surface of the biconvex lens, then ratio of radius of curvature of front and back surface of the biconvex lens is ____________.
