  The conventional picture for the origin of the polarization of a supernova is
based on a model of Thomson or resonance scattering of photons traveling
through an aspherical supernova atmosphere. Positive detection of intrinsic
polarization in SN 1987A is then interpretated as evidence of an asymmetrical
supernova atmosphere. We show here a different view based on the scattering of
the supernova light by a dusty circumstellar material (CSM), or the ``light
echo'' effect. At a given epoch after the explosion, the observed photons
consist of both those propagating directly from the supernova and those
scattered by dust particles in the CSM. Polarized light can be produced if the
distribution of the dust particles is aspherical. The model can reproduce both
the time evolution of the observed broad band polarization of SN 1987A and
major features of the polarization spectra. It is also successful in providing
a natural model for the early infrared light curve, in particular the observed
30 day delay of the IR maximum compared to the maximum of the bolometric light
curve.
