Domain: Natural Science — Physics
Target concept: The curved trajectory of a charged particle in the magnetic field within the detector model

Video generation prompt: Inside a transparent cylindrical detector, a particle source emits positively charged particles into a uniform magnetic field oriented out of the page, perpendicular to the front-view viewing plane. The magnetic field is then reversed to point into the page, and the particles are emitted again, demonstrating the trajectories of the particles in two successive emissions from the front view in an animation.

Evaluation guide:
(i) Target concept: Magnetic deflection of moving charges governed by the Lorentz force; curvature reversal upon B-field inversion. Minimum mechanism: the particle must carry positive charge; the B-field must be uniform and oriented perpendicular to the front-view plane (directed out of or into the page) so the resulting Lorentz force lies within that plane and produces a visible curved path; motion must be non-relativistic and confined to a 2D projection; the detector must stay static and optically transparent so the front view is unobstructed.
(ii) Storyline: [Phase 1] A stable front-view shot establishes the transparent cylinder with the source centered inside it; the out-of-page field is shown with dot symbols spread across the interior. [Phase 2] Particles emit from the source and trace a smooth, continuous circular arc bending in one rotational sense, staying inside the cylinder. [Phase 3] The field symbols switch from dots to crosses, signaling reversal to into-the-page; no camera or object movement occurs. [Phase 4] Identical particles emit again from the same source and trace a circular arc bending in the opposite rotational sense, matching the first arc's scale and containment. [Phase 5] The final frame holds both arcs on screen together, or fades cleanly with no third emission, no overlay distortion, and no depth ambiguity; all events stay coplanar and front-facing.

Manual:
Experimental Procedure
1. Position the particle source at the center of the transparent cylindrical detector.
2. Apply a uniform magnetic field directed out of the page (perpendicular to the front-view plane) inside the cylinder.
3. Emit positively charged particles from the source; observe the curved trajectory from the front view.
4. Reverse the magnetic field direction so it now points into the page.
5. Emit identical particles again from the same source; observe the reversed curvature from the same front view.
Observation of Experimental Phenomena
In the first emission, particles follow a smooth circular arc bending in one rotational sense (e.g., clockwise). In the second emission, particles follow a smooth circular arc bending in the opposite rotational sense (e.g., counterclockwise), with the same curvature magnitude and origin point as the first.
Summary of Experimental Principles
Charged particles experience a Lorentz force F = q(v × B). For a positive charge and a uniform B field oriented perpendicular to the plane of motion, the trajectory is a circle lying in that plane. Reversing B reverses the force direction and therefore the curvature's rotational sense — demonstrated here through front-view observation of two successive emissions.

Prompt Grounding rubric:
level_1: No transparent cylindrical detector is visible; or no particle source is present; or no field-orientation symbol (dots, crosses, or arrows) appears anywhere in the frame; or no particles are ever emitted from the source; or the shot is not a front-on view of the cylinder's axis.
level_2: A container appears but is misshapen or opaque rather than a clear cylinder; the particle source is visible but sits off the cylinder's central axis; a field symbol is shown but is not marked as out-of-page (dots) during the first emission; the camera view is oblique or top-down instead of a stable front-facing shot perpendicular to the cylinder's axis.
level_3: The transparent cylindrical detector is correctly shaped and fully visible; the particle source sits at the center of the cylinder; particles are visibly emitted from the source in the first pass; the camera holds a stable front-view angle orthogonal to the cylinder's axis; the field is marked with dot symbols spread across the interior during the first emission, indicating an out-of-page orientation.
level_4: Everything described at the 3-point level is present; in addition, the field symbols visibly switch from dots to crosses before the second emission begins, signaling the field reversing to into-the-page; the second emission starts from the same source location as the first; both emissions occur within one continuous shot with no cut or repositioning of the detector.
level_5: Everything described at the 4-point level is present; in addition, both emissions play out in a single unbroken take; the cylinder does not shift position within the frame; the particle source stays at the same location for both emissions; the front-view framing shows no perspective drift, zoom, or rotation for the entire duration.

Scientific and Causal Correctness rubric:
level_1: In both emissions, particles travel in straight, non-curving lines regardless of whether the field symbols show dots or crosses; there is no distinguishable difference in path shape between the first and second emission; particles move radially outward from the source with no visible bending at all.
level_2: Trajectories show some curvature, but it contradicts the expected relationship between the displayed field symbol and a positive charge's motion: e.g., the first emission (marked out-of-page with dots) curves counterclockwise instead of clockwise, or the second emission (marked into-page with crosses) curves the same rotational sense as the first instead of reversing; or the curvature radius changes drastically between the two emissions with no change in the field symbols to justify it; or a particle's arc disappears mid-path and reappears elsewhere in the detector.
level_3: The first emission traces a circular arc curving in one rotational sense (e.g., clockwise) while dot symbols mark the field as out of the page; the second emission, after the symbols switch to crosses (into the page), traces an arc curving in the opposite rotational sense (e.g., counterclockwise); both arcs originate from the same source point and stay within the cylinder; neither emission shows a straight-line path.
level_4: Everything described at the 3-point level holds; in addition, the curvature reversal exactly tracks the dot-to-cross field-symbol switch: clockwise while the field is marked out of the page, counterclockwise once it is marked into the page; no arc crosses or penetrates the cylinder wall; both arcs stay smooth and continuous with no kinks or breaks partway along the path.
level_5: Everything described at the 4-point level holds; in addition, the two arcs share the same radius of curvature, with neither emission bending noticeably tighter or looser than the other; both arcs lie flat within the front-view plane with no apparent depth or out-of-plane drift; no extra or duplicate particle paths appear beyond the two intended arcs.

Spatiotemporal Consistency rubric:
level_1: The cylindrical detector's shape visibly deforms: stretching, shearing, or flickering between frames; the particle source jumps to a different position between the two emissions; a particle's arc appears or disappears abruptly mid-path instead of drawing continuously; the illumination on the cylinder swings unpredictably between bright and dark; the camera angle wobbles or cuts partway through the sequence.
level_2: The cylinder keeps its overall shape, but its transparency flickers on and off, or its outline pulses; the particle source appears to vibrate or change size between the two emissions; the drawing of an arc visibly pauses partway through and resumes after a delay; the field symbols or the cylinder's edge shimmer noticeably during the transition between the two emissions.
level_3: The cylinder stays rigid and evenly transparent for the whole sequence; the particle source remains at one fixed spot; each arc is drawn continuously from the source to its endpoint without pausing or restarting; the overall lighting on the scene stays steady; the camera's position and framing do not shift between the first and second emission.
level_4: Everything described at the 3-point level holds; in addition, the particles move at a smooth, even pace with no sudden jerks, freezes, or speed-ups along either arc; each arc connects cleanly from the source to its endpoint with no visible gap or overlap; the arcs show no warping or perspective distortion as the particles travel along them.
level_5: Everything described at the 4-point level holds; in addition, the particle motion along both arcs looks completely fluid, with no stutter or inconsistent blurring between frames; the arcs' edges look smooth rather than jagged or blocky; the dot-to-cross field-symbol switch and the start of the second emission occur back-to-back with no unexplained pause between them.