Domain: Natural Science — Physics
Target concept: Superposition of Water Waves

Video generation prompt: Two circular water waves of the same frequency and equal amplitude are generated in a wave tank, and they propagate toward each other along the same line. The waveform changes after the two waves meet are captured from above.

Evaluation guide:
(i) Target concept: Linear superposition of coherent mechanical waves in 2D medium
Minimum mechanism: Two spatially separated, phase-locked, monofrequency point sources emitting isotropic waves into a homogeneous, low-damping shallow-water medium; observation plane orthogonal to propagation direction; no boundary reflections dominating the field during interaction window.
(ii)Storyline: [Phase 1] Two identical point sources activate simultaneously → circular wavefronts emerge centered at respective source locations. [Phase 2] Wavefronts expand radially and symmetrically, maintaining circular shape and constant speed. [Phase 3] Fronts approach each other along the shared centerline; distance between leading edges decreases continuously. [Phase 4] Leading edges meet at midpoint → overlapping region forms and grows; interference pattern emerges exclusively within overlap zone. [Phase 5] Pattern stabilizes: high-amplitude antinodes and zero-amplitude nodal lines become clearly resolved and persist while overlap continues. Perspective constraint: strictly top-down, fixed camera; visibility constraint: entire tank surface and both sources must remain fully in-frame without occlusion or cropping at all times.

Manual:
Experimental Procedure
1. Fill shallow rectangular wave tank with clear water to uniform depth.
2. Activate two identical point-wave generators simultaneously at fixed positions on opposite sides of tank centerline.
3. Record from directly overhead for 10 seconds, capturing wave initiation, propagation toward each other, and mutual overlap.
Observation of Experimental Phenomena
Two expanding circular wavefronts travel along the same straight line, meet at the tank center, and form a stable interference pattern: alternating concentric zones of larger ripples (constructive interference) and flatter surface (destructive interference) persisting only where waves overlap.
Summary of Experimental Principles
When two coherent circular waves of equal amplitude and frequency meet, superposition causes constructive interference where path difference = nλ and destructive interference where path difference = (n+½)λ, producing a stationary interference pattern along their line of propagation.

Prompt Grounding rubric:
level_1: No wave tank or water surface visible; no circular wave crests present; only one wave source (or none) is shown; the camera view is not from directly above; the two wave patterns never travel toward each other along a shared line.
level_2: A wave tank with water is shown, but the wave activity is essentially static or only a single expanding circular ripple from one source is visible; the second source is missing or produces no visible waves; the camera angle is oblique or side-on rather than overhead; the two disturbances do not travel toward a shared meeting point.
level_3: An overhead shot shows a wave tank with two distinct point sources positioned on opposite sides of a shared centerline; each source emits an expanding circular ripple pattern; the two ripple fronts travel toward each other along that centerline; the region where they will meet is visible within the frame.
level_4: Everything in score 3 is present, plus both sources stay fixed at their original positions for the whole clip; each ripple front keeps an unbroken circular shape as it grows; the two fronts visibly close the gap between them along the centerline until their edges touch; no unrelated props, on-screen text, or graphic overlays appear over the tank.
level_5: Everything in score 4 is present, plus the two sources are matched in visible size and mirror-positioned left and right of the tank's center; both expanding ripple sets stay on screen continuously from the moment they appear until their fronts fully overlap; no frame shows a ripple front cut off by the tank edge or frame boundary; the whole sequence from first ripple to full overlap plays out in one uninterrupted overhead shot, with no cut, zoom, or camera reposition.

Scientific and Causal Correctness rubric:
level_1: At the overlap region, the two ripple sets cross without any visible amplitude change — no patch of the surface ripples higher or sits calmer than its surroundings; the waveform looks the same whether or not the fronts have met.
level_2: The two ripple fronts reach each other, but one visibly swamps or hides the other rather than the two coexisting; the overlap zone shows a uniform ripple height with no patches of stronger or weaker disturbance.
level_3: Where the two ripple sets overlap, the surface visibly separates into an alternating pattern of stronger ripples (crests reinforcing) and calmer patches (crests and troughs canceling); this alternating pattern is confined to the overlap zone and holds steady for as long as both wave trains are present there.
level_4: Everything in score 3 is present, plus the calmer (near-still) patches trace out curved bands bowing outward from the midpoint between the two sources, resembling the hyperbola-shaped fringes of a classic two-point ripple-tank pattern, with the strongest-ripple patches sitting between them; only the single band running straight along the perpendicular bisector between the two sources is a straight line, the layout is symmetric about that bisector, and no stray disturbed patches appear outside the overlap zone.
level_5: Everything in score 4 is present, plus the curved calm bands and the strong-ripple bands between them stay sharply distinguishable throughout the full overlap window, with the ripple height at the strong bands clearly and visibly greater than in either wave train alone; the pattern shows no fading, no lag between the two wave trains, and no drift in the position of the bands while the sources keep emitting.

Spatiotemporal Consistency rubric:
level_1: A wave source or ripple front vanishes and reappears without traveling there; the water surface flickers or resets to still mid-clip; the overall scene lighting suddenly changes; the tank's edges warp or disappear; the ripple motion freezes or jumps abruptly.
level_2: One ripple front visibly speeds up or slows down relative to the other; a source's position shifts partway through the clip instead of staying put; the water's surface texture switches abruptly (e.g., from rippled to glassy smooth) without a gradual transition; a shadow on the tank jumps to a new spot instantly; the tank's outline bends or flexes while the waves move.
level_3: Each ripple front grows outward continuously and smoothly from its own fixed source, with no source or wavefront jumping to a new spot; the water's surface texture and the way it reflects light look the same from start to finish; the tank's rim stays rigid, straight, and fully in view the whole time.
level_4: Everything in score 3 is present, plus each ripple front expands as a clean, unbroken circle with no kinks, sharp corners, or angular breaks in its edge; there is no ghosting, tearing, or motion-blur smearing that hides the ripple shape from moment to moment; the tank and water surface never bend, buckle, or otherwise change shape.
level_5: Everything in score 4 is present, plus the ripple motion plays smoothly with no stutter, no repeated or frozen frame, and no visible interpolation glitches; the wavefront edges stay crisp rather than turning fuzzy or noisy; the overhead framing shows no drifting or wobbling perspective; the tank's water surface stays visibly flat, without any dips, bulges, or warps a viewer could notice by eye.