  We revisit the total scatterings (in terms of extinction, scattering and
absorption cross sections) by arbitrary clusters of nonmagnetic particles that
support optically-induced magnetic responses. Our reexamination is conducted
from the perspective of the electromagnetic duality symmetry, and it is
revealed that all total scattering properties are invariant under duality
transformations. This secures that for self-dual particle clusters, the total
scattering properties are polarization independent for any fixed incident
direction; while for non-self-dual particle clusters, two scattering
configurations that are connected to each other through a duality
transformation would exhibit identical scattering properties. This
electromagnetic duality induced invariance is irrelevant to specific particle
distributions or wave incident directions, which is illustrated for both random
and periodic clusters.
