Context: This simulator models a collimated beam entering a parallel plate at 45° angle of incidence (air -> filter -> air). The output value is lateral beam shift in mm, not wavelength shift.
Controls how much the beam bends inside the filter. Typical optical glass is around 1.45 to 1.80.
Physical plate thickness along the surface normal. Larger thickness produces larger lateral shift.
Light Shift: —
Diagram guide: dark line = beam path, orange double arrow = lateral shift between incident and emergent beams.