# Refuse an aliased physical sampling request
Preflight a 40 kHz plane wave in air on a two-metre, 200-by-200 grid. Strict
sampling rejects the request before allocating field storage and returns the
certificate that explains both carrier and squared-magnitude fringe
under-resolution.
The certificate applies to a homogeneous, isotropic, three-dimensional scalar
free-field model. Squared magnitude is a normalized observable, not physical
intensity, power, or energy; polarization, impedance, interfaces, obstacles,
and diffraction remain outside scope.