  The exact finite-size spectra for several quantum impurity models related to
the Kondo problem are obtained from the Bethe ansatz solutions. Using the
finite-size scaling in boundary conformal field theory, we determine various
surface critical exponents from the exact spectrum, which accord with those
obtained by Affleck and Ludwig with Kac-Moody fusion rules. Some applications
to critical phenomena observed in connection with the orthogonality catastrophe
are also discussed.
