Domain: Engineering — Optical Engineering
Target concept: Young's Double-Slit Interference Experiment

Video generation prompt: On the Young's double-slit interference experimental setup, a monochromatic red light source (λ = 630 nm) is incident on a single slit and then passes through a double-slit (slit separation d = 0.2 mm). A white screen is placed behind the double-slit. The light source and double-slit are aligned coaxially. Interference fringes are observed on the screen, with bright fringes marked in red and dark fringes marked in black. The fringe spacing is indicated by white scale markings.

Evaluation guide:
(i) Target concept: Linear, high-contrast, monochromatic double-slit interference pattern formed by coherent red light on a matte white screen under fixed coaxial geometry.
Minimum mechanism: Light must be spatially filtered (single slit) to achieve sufficient coherence; double-slit must produce two mutually coherent wavefronts; screen must be stationary and perpendicular to beam axis; fringes must arise exclusively from superposition, not diffraction alone.
(ii)Storyline: [Frame 0–2] Red light source activates → beam propagates straight → illuminates single slit → beam narrows. [Frame 3–5] Narrowed beam reaches double-slit → splits into two coherent beams → beams diverge symmetrically. [Frame 6–10] Two beams overlap on white screen → stable interference pattern emerges: central red bright fringe appears first, followed symmetrically by alternating red/black fringes; white scale markings remain fixed and co-aligned with fringe direction throughout. Perspective is fixed frontal view; all objects fully visible in frame; no occlusion; screen fills lower 60% of frame; slits occupy upper 30%; light source is top-center, emitting downward.

Manual:
Experimental Procedure
1. Activate monochromatic red light source (λ = 630 nm).
2. Light passes through single slit, then double-slit (d = 0.2 mm), aligned coaxially.
3. Interference pattern forms on white screen placed behind double-slit.
Observation of Experimental Phenomena
- Alternating red bright fringes and black dark fringes appear on screen.
- Fringes are equally spaced and parallel to each other.
- White scale markings indicate fringe spacing along fringe direction.
Summary of Experimental Principles
- Coherent red light diffracts at single slit, then interferes after passing through two narrow, closely spaced slits.
- Path difference determines constructive (red) and destructive (black) interference positions.
- Fringe spacing ∝ wavelength / slit separation — verified qualitatively by uniform red/black banding.

Prompt Grounding rubric:
level_1: None of the required optical elements are recognizable: no red light source, no single slit, no double-slit aperture, no white screen, and no bright/dark banding of any kind appears anywhere in the frame; the scene does not resemble a double-slit interference setup at all.
level_2: At most one or two elements appear in a generic form (e.g., an undifferentiated glow or a blank rectangle standing in for the screen), but the double-slit aperture is missing or wrongly shaped (a single opening, a round hole, or three or more openings), the screen is not positioned behind the double-slit along the beam path, no white scale markings appear near any banding, and any visible banding is unstructured rather than an ordered set of parallel bands.
level_3: A reddish light source, a single slit, a double-slit formed by two narrow parallel openings, a white screen behind the double-slit, and white scale markings are all present and recognizable, and the beam's centerline visibly runs from the source through the single slit, through the double-slit, and onto the center of the screen; however the banding on the screen does not follow the red/black scheme (e.g., every band is the same color, or the bands use colors other than red and black).
level_4: All five elements (red source, single slit, double-slit, white screen, scale markings) are present, correctly shaped, and coaxially aligned along the beam path, and the screen shows alternating red bright bands and black dark bands; but a viewer would notice a visible flaw at a glance: for example neighboring bright bands are clearly unequal in width, the red on some bands looks washed out or pink toward the frame edges, or some dark bands read as dark gray or brown rather than black.
level_5: All five elements are present, correctly shaped, and coaxially aligned; the white scale markings sit alongside the fringes and stay evenly spaced with them; every bright band reads as a uniform saturated red across its width and every dark band reads as a uniform black, with band widths that look equal to one another by eye across the visible screen; no stray graphic elements (labels, arrows, glare, reflections) intrude on the pattern.

Scientific and Causal Correctness rubric:
level_1: The bright/dark banding on the screen has no traceable cause from the optics: it appears before the beam reaches the double-slit, persists even with the beam path to the double-slit effectively blocked, or changes with no relation to the beam reaching the apertures at all; i.e., the pattern is not produced by light passing through the single slit and then the double-slit.
level_2: The banding is at least tied to the beam reaching the screen, but the apparatus as shown cannot produce genuine two-beam interference: the double-slit is effectively a single opening, a diffuser, or has more than two openings, so light does not travel along exactly two coherent paths from source to screen; any banding present therefore cannot be attributed to path-difference-driven superposition of two beams.
level_3: Two coherent paths are visibly established (the beam narrows at the single slit, then splits and re-diverges at the double-slit before the two parts overlap on the screen), and banding appears only once the double-slit is reached, with bright fringes red and dark fringes black overall; however the fringe sitting on the beam's central axis, where the two slit paths are equal in length, is dark rather than bright, or the red/black alternation is broken somewhere along the pattern (e.g., two red fringes appear in a row), so the expected path-difference progression is not consistently visible.
level_4: The full causal chain is visible and correctly ordered: light activates, narrows at the single slit, splits into two coherent beams at the double-slit, and only after the two beams overlap on the screen does banding appear; the central-axis fringe (equal path length from both slits) is bright red as constructive interference requires, and fringes alternate strictly red, black, red, black outward with spacing that looks constant step to step; one minor, non-defining anomaly remains, such as the outermost fringes appearing slightly dimmer than those near the center.
level_5: The full causal chain is visible and correctly ordered: light activates, narrows at the single slit, splits into two coherent beams at the double-slit, and only after the two beams overlap on the screen does banding appear; the central-axis fringe is the brightest red fringe present, consistent with constructive interference at zero path difference; fringes alternate strictly red, black, red, black outward with no skipped or doubled bands, and the spacing between successive bright fringes looks constant across the visible pattern, consistent with the path difference growing in equal steps with position, with no unexplained anomaly breaking this causal picture.

Spatiotemporal Consistency rubric:
level_1: The double-slit, screen, or scale markings vanish and reappear, jump to a new position, or change shape abruptly between frames (e.g., the double-slit's two openings separate or merge into one, the screen suddenly changes size, or the scale markings jump to a different location); the beam switches on and off discontinuously rather than staying lit once activated.
level_2: Nothing outright teleports or vanishes, but motion is visibly unsteady: the fringes visibly jump in position by more than about 10% of a fringe's width between frames, the beam flickers or strobes in brightness, fringe edges shimmer, dissolve, or reform, the screen surface appears to ripple or warp, or the scale markings visibly slide sideways between frames; alternatively, the video cuts between disconnected moments (e.g., jumping straight from the setup stage to a fully formed fringe pattern with no visible transition).
level_3: All optical elements stay within one continuous scene with no cuts, warping, or flicker; the beam is lit continuously once activated and the fringe pattern builds up gradually rather than snapping into existence; the scale markings stay attached to the screen and move with it; a small, easily overlooked amount of positional wobble (less than about 5% of a fringe's width) is visible in the fringe edges or beam outline from frame to frame, but nothing pops, jumps, or disappears.
level_4: All optical elements remain essentially rock-steady across the video: no visible wobble in fringe positions, the beam's width and direction do not drift, and the scale markings stay fixed relative to the screen with no perceptible sliding; the fringe pattern still builds up smoothly rather than snapping in; one small, non-disruptive imperfection remains, such as brief motion blur on the single-slit edges while the beam is stabilizing, that does not affect the visibility or position of any fringe.
level_5: Every element (light source, single slit, double-slit, screen, scale markings, and fringes) holds its size, shape, position, and orientation throughout with no visible drift, flicker, warp, or discontinuity; the beam stays uniformly lit once activated with no flicker or pulsing; the fringe pattern builds up as one smooth, continuous progression with no snapping or popping in; the entire scene reads as a single continuous, physically stable shot from a fixed viewpoint.