Domain: Engineering — Food and Bioprocess Engineering
Target concept: Detection of Vitamin A (Ultraviolet Fluorescence Method)

Video generation prompt: Take one drop of cod liver oil sample and place it into a quartz cuvette, then insert the cuvette into the sample chamber of an ultraviolet spectrofluorometer with the excitation wavelength set to 328 nm.

Evaluation guide:
(i) Target concept: Detecting vitamin A by ultraviolet-induced fluorescence requires a UV-transmitting quartz cuvette holding cod liver oil (a lipid-soluble source of retinol) positioned inside a spectrofluorometer's sample chamber, where a 328 nm UV excitation beam illuminates the sample and the retinol re-emits part of that absorbed energy as a longer-wavelength blue-green glow (around 470 nm), a Stokes-shifted fluorescence, not a simple reflection of the incident UV light. Minimum mechanism: the cod liver oil must read as a viscous, translucent golden-amber liquid; the cuvette must read as optically clear fused quartz rather than ordinary glass (which absorbs UV); the excitation beam must read as UV-specific (a dim violet or near-invisible light) rather than generic white light; and once illuminated, the sample must visibly emit a distinctly different-colored glow than the excitation beam itself.
(ii) Storyline: [Frame 0–3] Dropper tip approaches the cuvette opening → [Frame 4–6] A golden-yellow droplet detaches and settles at the cuvette's floor, forming a meniscus → [Frame 7–9] The cuvette is carried into the spectrofluorometer's sample chamber and the chamber door closes → [Frame 10] The UV excitation source switches on and the cod liver oil visibly glows blue-green against the surrounding chamber. All events occur in a fixed frontal view; the droplet must stay intact and unspread; the cuvette must stay upright; hands or tools must not dominate the frame; visibility prioritizes object identity, causal sequence, and the resulting glow over operator anatomy.

Manual:
Experimental Procedure
1. Take one drop of cod liver oil using a clean dropper.
2. Place the drop into a quartz cuvette.
3. Insert the cuvette into the sample chamber of a spectrofluorometer and set the excitation wavelength to 328 nm.
4. Switch on the UV excitation source and observe the light emitted from the sample.
Observation of Experimental Phenomena
A single golden-yellow translucent droplet rests at the bottom of a clear, colorless quartz cuvette; once the 328 nm UV excitation source is switched on, the droplet visibly emits a blue-green fluorescent glow that is clearly a different color from the dim violet excitation light itself.
Summary of Experimental Principles
Retinol (vitamin A) in cod liver oil absorbs ultraviolet light near 328 nm and re-emits part of that energy as fluorescence at a longer wavelength (around 470 nm, seen as a blue-green glow) — a Stokes-shifted emission used to qualitatively detect vitamin A. Quartz cuvettes are required because they transmit this UV excitation light, whereas ordinary glass absorbs it.

Prompt Grounding rubric:
level_1: No cod liver oil droplet, no quartz cuvette, and no spectrofluorometer housing are visible in frame; or the scene substitutes unrelated apparatus (e.g., a plastic vial, a household flashlight standing in for the UV excitation source, or a dropper releasing a liquid that is clear or dark rather than golden-amber); the take-place-insert sequence is absent or replaced entirely by text or a graphic overlay.
level_2: Exactly one of the three core elements is present (the cod liver oil droplet, or the quartz cuvette, or the spectrofluorometer housing) but the demonstration action is missing: the droplet never contacts the cuvette, or the cuvette never enters the instrument's sample chamber; taking, placing, and inserting are not shown as distinct depicted actions.
level_3: The cod liver oil droplet reads as a golden-yellow to amber translucent liquid; the cuvette reads as a transparent vessel with flat parallel walls (not curved like a test tube); the spectrofluorometer body is visible as a distinct benchtop instrument with a sample-chamber door; the droplet is shown detaching from a dropper and coming to rest inside the cuvette, and the cuvette is then shown being carried into and seated within the instrument's sample chamber; these two placement actions occur in that order without one substituting for the other.
level_4: Everything described for the 3-point level is still true, and beyond that: the droplet remains a single unbroken volume throughout (never shown as a smear, a puddle, or multiple separate droplets), the cuvette stays upright while being carried and inserted, the sample-chamber door is shown fully closed once the cuvette is seated, and no incidental tools (gloves, tweezers, labels, cotton swabs) appear on screen during the take-place-insert sequence.
level_5: Everything described for the 4-point level continues to hold, and in addition: the droplet keeps a rounded, meniscus-bound shape on contact with the cuvette floor with no splash or spreading beyond that meniscus, the cuvette's exterior stays visibly clean (no fingerprint smudges or dust obscuring its walls), the instrument's control panel is visible and shows an active indicator (a lit power light or an idle readout) once the cuvette is seated, and the camera holds one fixed frontal framing for the entire take-place-insert sequence with no cuts, pans, or zooms.

Scientific and Causal Correctness rubric:
level_1: The instrument's illumination is shown as ordinary broad-spectrum white or yellow light rather than anything UV-specific, and the cod liver oil sample shows no light emission at all in response, or it appears to glow the exact same hue as the illuminating light itself (implying plain reflection, not a distinct emitted color); alternatively, detection is depicted through an unrelated method such as a color-changing chemical reagent or a test strip rather than any light-based reading.
level_2: An ultraviolet-styled excitation light is present (e.g., a dim violet or near-invisible beam distinct from household lighting), but the sample never visibly responds with any light of its own once illuminated, or the cuvette material looks like ordinary tinted glass rather than clear fused quartz, undermining the premise that UV light is reaching the sample; excitation and any apparent emission are not shown in a clear before/after order.
level_3: The cuvette reads as optically clear, colorless quartz rather than tinted glass, consistent with quartz's role in transmitting UV light that ordinary glass would absorb; the excitation source reads as UV-specific (a dim violet or near-invisible beam, not household white light); once the excitation source is shown active, the cod liver oil visibly emits a blue-green glow that is a distinctly different color from the excitation light itself, consistent with the Stokes-shifted fluorescence of retinol; this emission is shown only after, never before, the excitation source activates.
level_4: Everything true at the 3-point level still holds, plus: the emitted blue-green glow appears to originate specifically from within the oil droplet itself rather than from the cuvette walls, the chamber interior, or stray reflections, and the glow's brightness does not appear until the excitation source is unambiguously shown switched on (no glow visible during the earlier placement or insertion steps).
level_5: Everything true at the 4-point level still holds, plus: the space around the emitting droplet reads as noticeably dimmer than the glow itself (consistent with a darkened fluorometer chamber used to make weak fluorescence visible), and no ordinary white room lighting is shown illuminating the chamber at the same time as the UV excitation source, which would wash out or contradict a genuine fluorescence reading.

Spatiotemporal Consistency rubric:
level_1: The droplet appears already resting inside the cuvette with no dropper ever shown approaching or releasing it, or the cuvette appears already seated inside the spectrofluorometer chamber with no carrying or insertion motion shown; the droplet, cuvette, or emitted glow blinks in and out, changes size discontinuously between frames, or the room lighting jumps between bright and dark with no visible cause (e.g., no lamp, switch, or instrument activation shown triggering the change).
level_2: One major continuity break occurs: for example, the droplet-placement shot and the cuvette-insertion shot are filmed from mismatched angles or backgrounds as if spliced from two separate takes, the cuvette snaps from one orientation to another (e.g., rotating more than roughly 90° between frames) without passing through the motion in between, or the emitted glow appears at full brightness in one frame with no gradual onset after the excitation source is shown switching on.
level_3: The droplet stays adjacent to the dropper tip until it visibly detaches and settles in the cuvette, and the cuvette stays adjacent to the operator's hand until it is visibly seated in the spectrofluorometer chamber, with no jump cuts between these steps; any change in the scene's lighting (such as the chamber dimming or the sample beginning to glow) is shown as a gradual, continuous consequence of the excitation source being switched on rather than an unexplained cut; camera framing, background, and cast shadows stay geometrically consistent with a single fixed light source throughout.
level_4: Everything required at the 3-point level still holds, and further: the operator's hand (if visible) enters and leaves the frame smoothly with no sudden appearance or disappearance, the cuvette does not wobble or tip more than about 10 degrees while being carried or inserted, and the droplet's surface stays calm and undisturbed (no sudden ripple or jitter) from the moment it settles until the cuvette is seated in the instrument.
level_5: Everything required at the 4-point level still holds, and further: motion throughout the sequence reads as smooth with no stutter or strobing, motion blur on moving elements (hand, dropper, cuvette) stays consistent with their speed rather than mismatched between sharp and blurred elements in the same moment, and the relative depth ordering of dropper, droplet, cuvette, and instrument (what occludes what) stays coherent across the entire sequence with no foreground or background elements swapping apparent distance.