Domain: Natural Science — Physics
Target concept: Visible laser beam passes through an unpolarized cube beam splitter, generating...

Video generation prompt: In a dimly lit laboratory, a visible laser beam enters a non-polarizing cube beam splitter mounted on a support; a faint mist fills the air, and the beam splitter is gently rotated.

Evaluation guide:
(i) Target concept: Orthogonal beam splitting via a dielectric-coated cube interface under unpolarized illumination.
Minimum mechanism: The cube must contain a precisely oriented, partially reflective dielectric coating at its internal diagonal (hypotenuse) interface; the incident beam must strike this coating to trigger simultaneous transmission and reflection; mist must be present to scatter light and render the otherwise invisible beam paths visible in air; because it is the cube, not the laser, that rotates, the beam's angle of incidence on the internal coating changes continuously as the cube turns, and this changing angle is exactly what sweeps the transmitted and reflected beams through their arcs; the rotation shown must stay within a range where the beam still enters and exits through flat cube faces, avoiding grazing incidence or total internal reflection, so a clean two-beam split persists throughout.
(ii) Storyline: [Frame 0] A dim lab scene establishes ambient darkness; a monochromatic laser activates, projecting a straight beam toward the stationary cube; mist becomes visible as a translucent haze around the beam path. → [Mid-sequence] The beam contacts the cube's face, instantly producing two new beams exiting orthogonal faces; both beams scatter visibly in the mist. → [During rotation] The cube rotates steadily around its vertical axis; the transmitted beam's endpoint traces a circular arc on the far wall; the reflected beam's endpoint traces an orthogonal circular arc on an adjacent wall; both beams' exit points stay fixed at the cube's faces even as their directions sweep. → [Visibility constraint] Every beam segment stays continuously visible in the mist: no occlusion by the support, no beam dropout, no thinning of mist that would weaken the scattering. → [Perspective constraint] A fixed camera viewpoint keeps the full cube, both output beams, and the supporting structure in a single frame without cropping or parallax distortion.

Manual:
Experimental Procedure
1. In a dimly lit laboratory, position a visible monochromatic laser so its beam enters one face of a non-polarizing cube beam splitter mounted upright on a stable support.
2. Introduce faint mist into the air volume surrounding the beam path.
3. Gently rotate the beam splitter about its vertical center axis while maintaining beam alignment.
Observation of Experimental Phenomena
- A single incident laser beam enters the cube.
- Two distinct output beams emerge: one transmitted straight through the opposite face, one reflected perpendicularly from the side face.
- Both beams are continuously visible along their full length due to scattering in the mist.
- As the cube rotates, the spatial positions of both output beams change synchronously and smoothly.
Summary of Experimental Principles
- A non-polarizing cube beam splitter divides an unpolarized incident beam into two orthogonally directed beams (transmitted and reflected) with fixed intensity ratio (~50:50), independent of polarization state. Rotation alters the orientation of the splitting interface, thereby redirecting both output beams predictably in space.

Prompt Grounding rubric:
level_1: No visible laser beam is present, no cube-shaped beam splitter is shown, no mist is visible, no rotation occurs, and the lab does not read as dimly lit; none of the posted_prompt's core elements appear.
level_2: At least one core element appears (for instance, a cube-shaped object or a light source), but the laser beam is not a coherent colored beam (e.g., it reads as plain white light rather than a collimated red or green beam), the beam splitter is not clearly cube-shaped or not mounted on a support, no mist is visible, and the cube does not rotate; several required prompt elements are still missing.
level_3: A visible, coherently colored laser beam enters a cube-shaped beam splitter that sits on a visible support in a dim room; faint mist is present; the cube rotates; every core element and action from the posted_prompt appears, but the beam's alignment with the cube's faces, or the mist's density, looks somewhat off from what a real beam path would look like.
level_4: Every posted_prompt element is present and plausibly rendered: a collimated, single-colored laser beam (e.g., red or green) travels in a straight line into the cube; the cube beam splitter has an accurate cube shape with equal square faces and sits visibly mounted on a stable support; the room reads convincingly dim with low ambient light; faint mist is spread fairly evenly through the air around the beam's path; the cube rotates smoothly and continuously about a fixed center; no element is missing, misshapen, or frozen when it should move.
level_5: All 4-point conditions hold, and additionally: the cube's rotation is visibly centered on its own geometric center, with no wobble or off-axis drift; the mist stays faint and evenly present around the entire beam path both before and after it splits; the beam's color, brightness, and narrow collimated width stay constant through the rotation; and no stray object, reflection, or lighting artifact in the shot contradicts the posted_prompt's description.

Scientific and Causal Correctness rubric:
level_1: No scientifically plausible splitting behavior appears: for example, the beam passes straight through with no second beam at all, splits into three or more beams, disappears, only reflects with no transmitted beam, or shows a behavior that depends on beam polarization (such as vanishing at particular rotation angles), any of which would contradict a non-polarizing cube beam splitter's physics.
level_2: The beam reaches the cube but fails to produce two clearly separated output beams: for instance, only one output beam is visible, the two outputs overlap into one visible path, or both beams appear to exit the same face instead of two different faces; the mist fails to reveal the beam paths; and rotating the cube produces no visible change in where the output beams go.
level_3: Two distinct output beams appear, one continuing straight through the cube (transmitted) and one exiting at a right angle (reflected), each leaving from a different cube face; the mist makes both beams visible along their length; rotating the cube visibly moves both output beams; the count, directions, and rotation response are correct, but one or both beams occasionally flicker, briefly vanish, or fade out along part of their length due to uneven mist.
level_4: Both the transmitted and reflected output beams stay visible along their whole length in the mist for the entire shot; the transmitted beam exits the face opposite the input, continuing in the same direction as the input beam; the reflected beam exits the side face at a right angle to the input; as the cube rotates, the angle at which the beam strikes the internal coating changes smoothly, and both output beam endpoints sweep across their target surfaces in a matched, synchronized way with no jump, misalignment, or unphysical bending, all consistent with an unpolarized beam meeting a non-polarizing cube beam splitter's internal coating.
level_5: All 4-point conditions hold, and additionally: the point where the input beam meets the cube face looks sharp and undiffused rather than smeared; no third stray beam, ghost reflection, or internal glow appears; the transmitted and reflected beams look comparably bright, with neither one so dim it seems to vanish or so bright it visually swamps the other; and both beams keep a consistent, roughly round, tightly collimated cross-section before and after the split, with nothing suggesting polarization-dependent behavior in what should be a non-polarizing splitter.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal breaks: the beam jumps instantly from one path to another instead of moving continuously; the beam splitter appears to come apart and reassemble; the mist appears or disappears between one frame and the next; the room's lighting suddenly changes brightness; or the cube's shape visibly stretches, shears, or loses one of its flat faces.
level_2: Noticeable but less severe breaks: the beam's visible path is interrupted for a moment and reappears in a shifted position; the support holding the beam splitter appears to detach and reattach; the mist's density changes abruptly with no clear cause (like a sudden draft); or the lighting flickers enough that beam visibility clearly comes and goes across the shot.
level_3: All objects keep their spatial relationships stable: the cube stays rigidly fixed to its support; the mist fills the air around the setup steadily; the beam's entry point stays fixed at the laser's aperture; the two output beam endpoints move only because the cube is rotating; nothing floats free, stretches, rescales, or jumps in perspective.
level_4: All 3-point conditions hold, and additionally: the cube's rotation looks smooth and continuous, without jerks, stutters, or skipped frames; as the cube turns, the beam geometry changes gradually rather than snapping between a few fixed orientations; and the shadows or light falling on the support and surroundings stay physically sensible: no impossible double shadows, and no ambient light visibly leaking through what should be opaque mist.
level_5: All 4-point conditions hold, and additionally: the motion of the beam endpoints across frames matches what a rigidly rotating cube would produce; there's no visible strobing, shimmering moiré pattern, or shutter-related skew in the beam or mist; any visible drift of mist particles looks slow and calm, matching a still lab with no strong airflow; and there's no depth error: for example, no part of a beam that should be hidden behind the cube or support becomes visible.