Domain: Natural Science — Physics
Target concept: Visible Light Spectrum Color Mixing Experiment (Red + Blue)

Video generation prompt: Take the red and blue laser sources, adjust the optical path so that the two beams overlap on a white screen, and observe the color in the overlapping region.

Evaluation guide:
(i) Target concept: Additive color mixing of monochromatic red and blue light sources resulting in magenta in the region of spatial superposition.
Minimum mechanism: Two narrowband light sources emitting predominantly in ~630–680 nm (red) and ~450–495 nm (blue) ranges must illuminate the same area of a spectrally neutral (white/diffuse) surface; human photopic vision integrates the combined spectral power distribution as magenta.
(ii)Storyline: [Phase 1] Red laser source and blue laser source are visibly present and stationary, each emitting a collimated beam. [Phase 2] Both beams travel uninterrupted toward a static white screen. [Phase 3] Beams converge and intersect at a shared point/region on screen. [Phase 4] At intersection, a contiguous purple/magenta region appears, exclusively where beams co-illuminate. [Phase 5] Outside intersection, red beam retains red hue and blue beam retains blue hue; no color leakage or blending beyond overlap. Perspective is fixed frontal view; entire setup (sources, beams, screen, overlap) remains fully visible and unoccluded throughout.

Manual:
Experimental Procedure
1. Place red laser source and blue laser source side-by-side, aimed at a white screen.
2. Adjust alignment so red and blue beams strike same location on screen.
3. Observe color where beams overlap.
Observation of Experimental Phenomena
The overlapping region appears purple/magenta; the non-overlapping portion of the red beam remains red; the non-overlapping portion of the blue beam remains blue.
Summary of Experimental Principles
Red and blue light are primary additive colors; when superimposed, they produce magenta via additive color mixing in the visible light spectrum.

Prompt Grounding rubric:
level_1: No red laser source is visible; or no blue laser source is visible; or no white screen is visible; or no region where the two beams overlap is shown on the screen; or the beams are not both aimed at the screen at all.
level_2: Both a red laser source and a blue laser source are visible, a white screen is visible, and some overlap region appears on the screen, but the two beams do not come from two separate, spatially distinct sources (e.g., they emerge from one merged housing); or the screen is not a plain flat white surface (e.g., colored, patterned, or curved); or the overlap region is a single solid-colored spot rather than the visible convergence of two separate beams.
level_3: A red laser source and a blue laser source are both visible in the shot; a white screen is visible; two separate beams are visible traveling from the sources toward the screen; the beams visibly converge and overlap somewhere on the screen; the full setup described (two distinct sources, a shared screen, a visible overlap) is present and spatially coherent.
level_4: All conditions for the 3-point level are met, AND the red source visibly emits only red light and the blue source visibly emits only blue light with no color swap between them; the two beams keep separate, visible paths all the way up to the point where they meet; the overlap region forms one continuous patch on the screen rather than a broken-up or flickering scatter of spots; no extra light source, hand, or object blocks either beam's path or the screen.
level_5: All conditions for the 4-point level are met, AND the two laser sources are shown as clearly separate physical devices (distinct housings or otherwise visually distinguishable from one another); each beam is shown as one continuous, unbroken line from its source to the screen; the region where the two beams cross sits at the point where the two beam paths visibly meet, with no visible gap or offset between the beams' paths and the overlap patch.

Scientific and Causal Correctness rubric:
level_1: The overlap region is not purple/magenta at all: for example it looks black, gray, white, or green; or the beam color outside the overlap is wrong (e.g., the red beam looks orange or the blue beam looks cyan); or there is no visible color change anywhere the beams meet.
level_2: The overlap region does look purple/magenta, but something else is scientifically wrong: the beam color outside the overlap is off (e.g., the red beam reads as pink or the blue beam reads as violet), or the overlap patch clearly contains patches of green or yellow within it, or the purple color at the overlap flickers between purple and some other hue over the course of the video.
level_3: The overlap region reads as a steady purple/magenta color for the whole video; the part of the red beam outside the overlap stays visibly red; the part of the blue beam outside the overlap stays visibly blue; the purple color appears only in the region where the two beams cross, with nothing in the video contradicting this outcome.
level_4: All conditions for the 3-point level are met, AND the purple overlap region looks like one even color rather than a reddish patch on one side and a bluish patch on the other; the red and blue beams outside the overlap keep a consistent, saturated color with no washed-out or faded segments; there is no stray color fringe (such as a cyan edge on the red beam or a magenta edge on the blue beam) anywhere along either beam.
level_5: All conditions for the 4-point level are met, AND the overlap region's purple color is visually indistinguishable from a standard magenta: it shows no perceptible greenish or yellowish tint anywhere within it; the red beam shows no visible tinge of blue or green outside the overlap, and the blue beam shows no visible tinge of red or green outside the overlap; the boundary between the red-only, blue-only, and purple regions is clearly defined and lines up with where the beams visibly cross.

Spatiotemporal Consistency rubric:
level_1: The beams appear or disappear abruptly with no visible travel between frames; or the screen shifts, rotates, or jumps position; or either laser source moves in a way that skips over positions instead of changing smoothly; or the purple overlap region appears on the screen before both beams have visibly reached it.
level_2: A beam's path visibly warps, bends, or breaks into disconnected segments; or the screen shows a sudden shift in lighting (e.g., a shadow or bright highlight jumps to a new spot); or a laser spot on the screen jitters sharply from frame to frame; or the purple overlap region flickers on and off with no connection to any visible movement of the beams; or one beam visibly reaches the screen well before the other with no visible reason.
level_3: Both beams travel continuously from their sources to the screen with no visible break, warp, or jump; the screen stays in the same position and orientation throughout; the purple overlap region only appears once both beams are visibly touching the screen; the red, blue, and purple regions are all visible together once the beams have converged, with none appearing out of step with the others.
level_4: All conditions for the 3-point level are met, AND each beam keeps a steady width along its length with no unnatural narrowing or widening; the screen's surface looks evenly lit with no localized glare or mirror-like reflection; no beam is clipped at the edge of the frame, no stray lens flare covers the overlap region, and no floating visual artifact appears near the beams or screen.
level_5: All conditions for the 4-point level are met, AND both beam paths stay straight and hold the same direction throughout the video with no visible curving or side-to-side drift; the screen stays flat and evenly bright across its whole visible surface; the purple overlap region appears at the point where the two beams visibly cross, with no visible delay between the beams' arrival and the region appearing.