  Scattering activities are generally manifest through different optical
responses of scattering bodies to circularly polarized light of opposite
handedness. Similar to the ubiquitous roles played by scattering theory across
different branches of photonics, scattering activities can serve as a
fundamental concept to clarify underlying mechanisms of various chiroptical
effects, both within and beyond scattering systems. In this work we investigate
scattering activities for reciprocal systems that exhibit various geometric
symmetries but are intrinsically achiral. We reveal how scattering activities
are generally bounded by reciprocity and parity conservation, demonstrating
that though extinction activity is usually eliminated by symmetry, scattering
activities in forms of distinct absorptions, scatterings or angular scattering
patterns can more widely emerge. Since our analyses are solely based on
fundamental laws of reciprocity and parity conservation, regardless of
geometric and optical parameters of the scattering systems studied, the
principles revealed are generically applicable. The intuitive and pictorial
framework we have established is beyond any specific coupling models, able to
reveal hidden connections between seemingly unrelated chiral manifestations,
and thus more accessible for a unified understanding of various chiroptical
effects.
