Domain: Natural Science — Physics
Target concept: Experiment on the Specular Reflection of Light

Video generation prompt: The laser beam emitted from the laser pointer is incident on a plane mirror. By adjusting the angle of incidence, the reflected light is directed along a fixed direction, and clear, focused light paths are formed at both the angle of incidence and the angle of reflection, making the propagation path of the light visible.

Evaluation guide:
(i) Target concept: Specular reflection of collimated light at a planar interface.
Minimum mechanism: A directional light source (laser) must emit a narrow beam that physically contacts a smooth, highly reflective planar surface, causing redirection of light energy along a second deterministic straight path governed by local surface normal geometry.
(ii)Storyline: [Frame 1–3] Laser pointer is held in hand, emitting a visible beam directed toward mirror; [Frame 4–6] Beam makes contact with mirror surface: incident path terminates cleanly at mirror; [Frame 7–10] Reflected path emerges instantly from same surface point and propagates in fixed direction; throughout, both paths remain simultaneously visible, spatially aligned, and geometrically consistent with planar reflection; viewpoint is static frontal/slightly oblique to resolve both paths and mirror surface without occlusion.

Manual:
Experimental Procedure
1. Hold a red laser pointer and aim its beam at the center of a vertically mounted plane mirror.
2. Adjust the laser angle until the reflected beam travels along a pre-marked fixed direction (e.g., toward a wall target).
3. Ensure smoke or dust is present to visualize both incident and reflected light paths.
Observation of Experimental Phenomena
Two straight, narrow, continuous light paths are simultaneously visible: one traveling from laser aperture to mirror surface (incident), and another traveling from mirror surface along a fixed direction away (reflected); both paths meet precisely at the mirror surface with no gap or offset.
Summary of Experimental Principles
The angle of incidence equals the angle of reflection; both angles are measured relative to the normal line at the point of incidence on a smooth, planar reflective surface.

Prompt Grounding rubric:
level_1: No laser pointer visible; no plane mirror present; no light path visible anywhere in the frame; none of the required objects (laser pointer, plane mirror, visible light path) appear.
level_2: At least one required object appears (e.g., laser pointer OR plane mirror), but no incident or reflected light path is visible; or light appears without a clear source or surface: no spatial association between laser, mirror, and light paths.
level_3: Laser pointer, plane mirror, and at least one visible light path (either incident or reflected) are all present and co-located in the same scene; however, either the incident path does not terminate at the mirror surface, or the reflected path does not originate from the mirror surface, or both paths are not simultaneously visible.
level_4: Laser pointer, plane mirror, and two distinct visible light paths (incident and reflected) are all present, co-located, and correctly spatially linked: incident path ends at mirror surface, reflected path begins at same mirror location; both paths are continuous and clearly separable; fixed-direction reflection is implied by path geometry but no explicit directional reference (e.g., target line or alignment marker) is required.
level_5: All elements from 4-score are present AND both light paths are simultaneously visible, sharply defined, and extend continuously from laser aperture → mirror surface → fixed output direction; laser pointer is held/stationary, mirror is rigidly mounted, and no extraneous light sources or scattering artifacts obscure the two clean paths.

Scientific and Causal Correctness rubric:
level_1: No causal relationship between laser emission and light path appearance; light paths appear without laser activation, or appear before laser points at mirror, or reflect from non-planar/non-mirror surfaces; incident and reflected paths show no angular correspondence (e.g., reflected path bends sharply or curves).
level_2: Laser is active and emits light, but light path does not contact mirror surface (misses entirely or terminates mid-air); or mirror is present but no reflection occurs; or reflected path originates from wrong location (e.g., edge, back, or off-surface point).
level_3: Incident path contacts mirror surface and a reflected path originates from that same contact point, but the two paths are not visually distinguishable as separate rays (e.g., merged into single diffuse glow, overlapping, or indistinct due to excessive scattering); or the reflected path deviates visibly from a straight-line continuation consistent with planar reflection (e.g., kinked, bent, or split).
level_4: Incident and reflected paths are two distinct, straight, non-overlapping light rays; both originate/terminate precisely at the mirror surface with no gap or offset; ray directions imply angular symmetry relative to surface normal (visually verifiable via path alignment and mirror orientation); no spurious secondary reflections or ghost paths appear.
level_5: All conditions from 4-score are met AND the incident and reflected paths maintain constant collimation and sharp focus throughout their visible length; no flicker, pulsing, or intensity decay along either path; no stray scatter halos or bloom that degrade path definition; path geometry remains stable and unchanging during the full clip duration.

Spatiotemporal Consistency rubric:
level_1: Objects teleport (e.g., laser pointer appears/disappears between frames); mirror changes position/orientation discontinuously; light paths blink on/off or jump positions without motion continuity; severe frame drops, warping, or structural tearing evident.
level_2: Minor object jitter or micro-teleportation (<10% of object size) occurs; light paths show intermittent visibility (on/off flicker across ≥3 non-consecutive frames); mirror surface shows inconsistent lighting/shadow across frames; one or more objects partially occlude themselves across frames.
level_3: All objects remain continuously visible and spatially coherent; light paths persist without interruption or blinking; mirror maintains fixed pose and position; no abrupt lighting shifts, shadow jumps, or perspective flips; minor inter-frame jitter or slight parallax drift is tolerated if objects retain relative spatial arrangement.
level_4: All conditions from 3-score are met AND light paths exhibit smooth, stable propagation with no strobing, pulsing, or intensity fluctuation; mirror surface reflects ambient light consistently; no inter-frame distortion (e.g., stretching, shearing, rolling shutter) affecting object shape or path geometry.
level_5: All conditions from 4-score are met AND the laser aperture, the mirror's point of incidence, and both beam endpoints stay visibly anchored at the same on-screen location across every frame, with no drift, jump, or offset perceptible by eye; motion blur never erases the beam's edges; the incident and reflected beams keep the same spatial alignment relative to the mirror and background throughout; and the mirror's highlight and beam brightness stay visually steady from the first frame to the last.