  We make use of the information obtained from semileptonic decays of $B$ and
$D$ mesons, within an effective lagrangian description based on heavy quark
theory and on chiral expansion, to study the radiative decays $B \to K^\star
\gamma$ and $B_S \to \phi\gamma$, and the pair conversion processes $B \to K
e^+e^-$ and $B \to K^\star e^+e^-$. We discuss with care the required
extrapolations from zero recoils. We obtain a BR($B\to K^\star\gamma$) between
$1.3\times 10^{-5}$ and $4.1\times 10^{-5}$ and BR($B_s \to\phi\gamma$) between
$1.4\times 10^{-5}$ and $4.5\times 10^{-5}$, with errors mainly arising from
the present uncertainty in the Kobayashi-Maskawa element $|V_{ts}|$. For the
pair conversion processes we study in particular the lepton effective mass
distributions whose measurements would allow for an understanding both long
distance and short distance contributions to such processes.
