Drag the apparatus. Watch the two waves' crests slide relative to each other as the path difference changes.
"Moving sensor" and "Fresnel biprism" aren't separate tabs — they're the exact same physics as Double Slit, just drag point P (or note: biprism uses two virtual sources instead of real slits, same Δ = d·y/D).
What is this?
Apparatus — drag the highlighted parts
Interference at the meeting point — which crest meets which
Wave 1 & Wave 2 — overlaid (do their crests line up?)
Resultant (Wave 1 + Wave 2) — what the receiver/screen actually gets