  Artificial gauge fields enable extending the control over dynamics of
uncharged particles, by engineering the potential landscape such that the
particles behave as if effective external fields are acting on them. Recent
years have witnessed a growing interest in artificial gauge fields that are
generated either by geometry or by time-dependent modulation, as they have been
the enablers for topological phenomena and synthetic dimensions in many
physical settings, e.g., photonics, cold atoms and acoustic waves. Here, we
formulate and experimentally demonstrate the generalized laws of refraction and
reflection from an interface between two regions with different artificial
gauge fields. We use the symmetries in the system to obtain the generalized
Snell law for such a gauge interface, and solve for reflection and
transmission. We identify total internal reflection (TIR) and complete
transmission, and demonstrate the concept in experiments. Additionally, we
calculate the artificial magnetic flux at the interface of two regions with
different artificial gauge, and present a method to concatenate several gauge
interfaces. As an example, we propose a scheme to make a gauge imaging system -
a device that is able to reconstruct (image) the shape of an arbitrary
wavepacket launched at a certain position to a predesigned location.
