Domain: Engineering — Optical Engineering
Target concept: Single-slit Diffraction Experiment

Video generation prompt: Set up a single-slit diffraction experimental setup, where a monochromatic blue light source (λ = 450 nm) is incident on a single slit (slit width a = 0.1 mm). A white screen is placed behind the slit to observe the diffraction pattern. The central bright fringe is marked in blue, the secondary bright fringes are marked in light blue, and the dark fringes are marked in black.

Evaluation guide:
(i) Target concept: Wave nature of light manifested as far-field interference pattern from confinement through sub-wavelength-scale aperture.
Minimum mechanism: Coherent monochromatic illumination incident on a single narrow slit produces a Fraunhofer diffraction pattern on a distant screen, characterized by a central maximum flanked by diminishing secondary maxima separated by minima, all governed by phase coherence and path-length differences across the slit aperture.
(ii)Storyline: Frame 1–2: Static wide shot showing blue light source, centered vertical slit, and white screen in collinear alignment. Frame 3–5: Light beam illuminates slit; no immediate pattern. Frame 6–7: Central blue fringe emerges sharply at screen center. Frame 8: First pair of dark fringes appears symmetrically left/right of center. Frame 9: First pair of light blue fringes appears outside dark fringes. Frame 10: Second pair of dark fringes and outer light blue fringes complete symmetric pattern; all elements remain fixed in viewpoint; no camera movement; no occlusion; full visibility of slit, beam path, and entire screen region containing pattern.

Manual:
Experimental Procedure
1. Align monochromatic blue light source directly in front of a narrow vertical slit.
2. Place white screen directly behind slit, centered on optical axis.
3. Illuminate slit with blue light; observe diffraction pattern on screen.
Observation of Experimental Phenomena
- Central bright fringe appears in pure blue, widest and most intense.
- Symmetric secondary bright fringes appear in light blue, decreasing in width and intensity outward.
- Dark fringes appear in pure black, separating all bright fringes.
Summary of Experimental Principles
Single-slit diffraction arises from Huygens-Fresnel principle: each point in slit acts as coherent wavelet source; destructive interference at angles where path difference = mλ yields dark fringes; central maximum occurs at θ=0 where all wavelets constructively interfere.

Prompt Grounding rubric:
level_1: No single-slit apparatus is visible: no blue light source, no narrow slit, no white screen, and none of the three prescribed fringe colors (blue central fringe, light-blue secondary fringes, black dark fringes) appear anywhere in the frame.
level_2: A single object type is recognizable (e.g., a light source, a slotted aperture, or a flat screen) but the set is incomplete or mislabeled: the light appears white or red instead of blue, the aperture is a hole or grid rather than a slit, or the screen shows no fringe pattern at all; no blue/light-blue/black color-coding is applied to any fringe.
level_3: The blue light source, the narrow vertical slit, and the white screen are all present in the correct front-to-back order (light → slit → screen), and the screen shows a central blue fringe with black dark fringes and light-blue secondary fringes, but placement is imperfect: the central fringe is noticeably off-center on the screen, the slit is not visibly narrower than the beam it emits, or a secondary fringe reuses the central blue instead of light blue.
level_4: The light source, slit, and screen are correctly scaled (the slit reads as far narrower than the screen, consistent with a 0.1 mm slit width); the pattern is centered on the screen with the blue central fringe widest, black dark fringes fully separating it from the light-blue secondary fringes on both sides, and left-right spacing is visually symmetric; one small setup flaw remains, such as faint color bleed at one fringe edge or slightly ragged slit edges.
level_5: The slit reads as a clean, thin vertical opening; the incident beam is uniformly blue and visibly confined to the slit's width with no stray light beside it; on the screen the three colors are clearly distinct with no muddying at any fringe boundary (pure blue center, light-blue secondary fringes, solid black dark fringes); the light–slit–screen arrangement reads as one coherent, correctly scaled optical bench with no extraneous props.

Scientific and Causal Correctness rubric:
level_1: The pattern contradicts single-slit diffraction outright: no central fringe forms, the center is darker than the flanks, or the fringe colors are scattered with no relation to alternating bright/dark bands.
level_2: At least three fringes are visible but core causal logic is violated: a light-blue secondary fringe is brighter or wider than the central blue fringe, a dark fringe shows color instead of black, or the order is reversed so light blue sits nearer the center than a dark band.
level_3: Fringes are ordered correctly outward from center (blue center → black → light blue → black → light blue …) and are left-right symmetric, but the intensity/width decay expected from sinθ ∝ mλ/a is not honored: e.g., the outer light-blue fringe looks as bright as the inner one, or dark fringes show a faint tint instead of solid black.
level_4: Each light-blue secondary fringe is visibly dimmer and narrower than the one closer to the central blue fringe, the black dark fringes show no color leakage, and fringe spacing widens slightly moving outward from the axis, consistent with the small angular spread a 0.1 mm slit produces with 450 nm light.
level_5: The full intensity envelope is faithful: the central blue fringe is unambiguously brightest and widest, each successive light-blue fringe outward is dimmer and narrower than its inner neighbor, dark fringes are solid black with no bleed, no extra bands appear beyond the first couple of orders, and color transitions at each fringe boundary are crisp rather than gradually blended.

Spatiotemporal Consistency rubric:
level_1: The apparatus falls apart in time: the slit, light source, or screen is missing from one frame and fully back in the next with no motion connecting the two, the screen appears rotated onto a different face with no turning motion shown, or the fringe pattern builds up out of order (an outer light-blue fringe appears before the central blue fringe).
level_2: The slit's width visibly changes partway through the clip, the screen shifts sideways or tilts out of its frontal plane, the beam switches on and off inconsistently, or fringes blink into and out of existence instead of building up continuously.
level_3: The light source, slit, and screen keep the same relative positions across the clip, and fringes build up from the center outward in the correct order, but a brief, minor hiccup occurs, such as a short stutter right as a new fringe pair appears or a momentary dip in contrast that quickly recovers.
level_4: The light–slit–screen arrangement stays rigidly aligned for the whole clip with no popping or stutter as new fringe pairs emerge, the screen's overall brightness stays even without flickering or shifting warmer/cooler, and none of the fringes show visible warping or stretching.
level_5: The slit, light source, and screen appear visually rock-steady for the full clip with no perceptible drift or wobble in their positions; the fringe pattern's growth from center outward is smooth with no strobing or skipped frames; the screen's illumination stays uniform edge to edge with no patchy hot spots that would break the pattern's left-right symmetry.