Domain: Natural Science — Atmospheric Science
Target concept: Simulate the formation of a rainbow, with the color bands clearly visible.

Video generation prompt: Dark background, a parallel white light beam is emitted horizontally from the left side, and a uniform water mist screen is formed in the beam's path using a spray bottle. The camera is fixed on the same side as the light source, angled to view the mist screen where the beam meets it.

Evaluation guide:
(i) Target concept: Formation of a primary rainbow via single internal reflection in water droplets.
Minimum mechanism: Incident white light must be collimated and monodirectional; water mist must consist of quasi-spherical droplets of sufficient density and uniformity to support coherent angular dispersion; observer must be positioned on the same side as the light source, looking into the mist, to receive the light that reflects back off the droplets at roughly 138° from the incoming beam.
(ii)Storyline: [Frame 1–3] Dark background established; white light beam appears horizontally from left edge. → [Frame 4–6] Spray activated; uniform mist screen forms in beam path, fully intercepting beam. → [Frame 7–10] Color bands emerge *only* within beam–mist intersection zone, forming a smooth, contiguous, circular arc with red outermost and violet innermost; arc remains stable and unbroken until end. Visibility constraint: All events must be fully visible within the fixed camera frame, positioned on the light-source side of the mist; no part of beam origin, mist screen, or rainbow arc may be cropped, occluded, or out-of-frame.

Manual:
Experimental Procedure
1. Set up dark background.
2. Position spray bottle in front of background, centered horizontally.
3. Emit horizontal white light beam from left side, aligned to pass through spray zone.
4. Activate spray bottle to form uniform water mist screen directly in beam path.
5. Capture the scene from a fixed viewpoint on the same side as the light source, facing toward the mist screen where the beam meets the droplets.
Observation of Experimental Phenomena
A continuous, curved arc of seven distinct, contiguous color bands (red, orange, yellow, green, blue, indigo, violet) appears exclusively where the white light beam intersects the water mist screen; red band is outermost, violet innermost; no color bands appear outside the beam–mist intersection zone.
Summary of Experimental Principles
White light disperses into its constituent wavelengths via refraction, internal reflection, and secondary refraction inside spherical water droplets; angular separation causes spectral bands to form a circular arc; dark background enhances contrast for band visibility.

Prompt Grounding rubric:
level_1: No dark background is shown; no horizontal white light beam is visible; no water mist screen appears; the camera viewpoint bears no clear relation to the light source and mist; none of the three core elements (dark background, white beam, mist screen) appear in a coherent arrangement.
level_2: Exactly one of the following is correctly present and placed: (a) a dark background, (b) a horizontal white light beam entering from the left, (c) a water mist screen positioned in the beam's path; the other two are missing or clearly wrong (e.g., the mist appears past where the beam would already have exited, the beam runs vertically, or the background is bright).
level_3: All three core elements are present: a dark background, a horizontal white light beam entering from the left, and a water mist screen sitting in the beam's path; the camera is fixed on the same side as the light source, angled toward the mist screen so the beam-mist meeting point is in view; nothing is cropped out of this framing.
level_4: Everything at the 3-point level holds, and in addition the light beam stays unbroken from its origin to the mist screen; the mist screen looks uniform across the beam's width (no visible clumping, gaps, or streaks); the beam's origin point stays at the left edge of frame; and the camera itself never pans, zooms, or repositions during the video.
level_5: Everything at the 4-point level holds, and in addition the beam shows no visible spreading or scattering before it reaches the mist; the mist blocks stray ambient light but lets the beam through cleanly (no glare or halo bleeding outside the beam's width); the dark background stays perfectly flat with no gradient or stray illumination; and the camera frame itself never shows any drift or shake, even at the edges.

Scientific and Causal Correctness rubric:
level_1: No color separation appears at all: no rainbow forms; every visible hue is a single color (e.g., everything stays white, or a uniform blue/gray tint) with no visible link between the beam-mist meeting point and any color pattern.
level_2: At least one colored band shows up, but not in rainbow (ROYGBIV) order, or the bands present skip around with visible gaps between them (e.g., only red and violet appear, nothing in between), or colors appear somewhere in the frame with no visible connection to where the beam meets the mist (e.g., a rainbow overlay that doesn't originate from the mist).
level_3: The color bands appear in correct spectral order (red on the outside, violet on the inside), sit right next to each other with no visible gaps, and appear only where the light beam meets the water mist screen; no stray color appears anywhere else in the frame.
level_4: Everything at the 3-point level holds, and in addition all seven bands of the visible spectrum (red, orange, yellow, green, blue, indigo, violet) can be made out at once, and none of the colors seen are ones that shouldn't be there (no pink, brown, or plain white patches breaking up the sequence).
level_5: Everything at the 4-point level holds, and in addition the band boundaries blend smoothly into each other, the way a real rainbow's spectrum does, with no hard edges or abrupt cutoffs between adjacent colors; the arc's curvature reads as a smooth, unbroken circular shape; red stays the outermost band and violet the innermost with no reversal anywhere along the arc; and the brightness fades gradually from the red/yellow side toward violet, without any color looking artificially oversaturated or clipped.

Spatiotemporal Consistency rubric:
level_1: The mist screen seems to snap into full existence, vanish, and reform without any spray building up gradually; the beam flicks on and off abruptly; the background jumps to a different look; or the camera view cuts between different vantage points mid-video.
level_2: The mist screen forms in visibly disconnected bursts with gaps in between rather than building up continuously, the beam wobbles sharply or changes direction partway through, the camera loses its fixed framing and visibly jitters, or the beam's path bends in a way a straight light beam never would before reaching the mist.
level_3: Nothing in the scene jumps position or vanishes and reappears; the camera never repositions; the beam stays straight and steady the whole time; the mist screen builds up and stays present continuously, without gaps in its visibility; the background stays the same throughout, and the beam, mist, and camera all keep the same relative arrangement from the first frame to the last.
level_4: Everything at the 3-point level holds, and in addition the lighting stays consistent: no sudden shadow shifts, no flare that turns on or off abruptly, no stray ambient light breaking in while the beam is active; the mist's density looks steady over time (it doesn't visibly thin, thicken, or pulse); and the beam's brightness stays constant with no flicker or fade.
level_5: Everything at the 4-point level holds, and in addition the background shows no visible shake or drift from one frame to the next; the beam, mist, and background all stay in the same relative position with no visible drift between them; the beam's motion looks physically continuous with no visible strobing; and there is no visible warping, stretching, or skewing of the scene's geometry across the video.