Domain: Natural Science — Physics
Target concept: A plane mirror forms a virtual image of the same size as the object, which is upright and laterally inverted relative to the object.

Video generation prompt: Position a book upright in front of a vertical plane mirror so that both the book and its reflection are visible in frame. Slowly move the book toward the mirror, then move it back to its starting position, while the camera and mirror remain fixed.

Evaluation guide:
(i) Target concept: Plane mirror image formation: a virtual image that is always the same size as the object, upright, and laterally inverted, located as far behind the mirror as the object is in front of it.
Minimum mechanism: The mirror is flat and specular; light from every point on the book reflects such that the virtual image forms as far behind the mirror plane as the book is in front of it; the reflection reverses the book's left-right orientation as seen by an observer while preserving its up-down orientation and overall size, regardless of the book's distance from the mirror.
(ii)Storyline: Frame 0–2: Book held upright at a short distance in front of the mirror; both the book and its mirror image are visible together in frame, appearing the same size. Frame 3–6: Book moves smoothly toward the mirror; its image inside the mirror appears to recede at a matching rate, so image and book stay equal in size to each other throughout. Frame 7–9: Book pauses close to the mirror; the image pauses at a correspondingly close position behind the mirror surface, still equal in size and laterally reversed relative to the book. Frame 10–13: Book moves smoothly back to (or past) its starting distance; the image recedes further behind the mirror by a matching amount. Throughout: the image remains upright and laterally inverted (e.g., any text or asymmetric marking on the book's cover reads mirror-flipped in the image); camera stays fixed, frontal, and wide enough to keep both book and full image in frame without cropping.

Manual:
Experimental Procedure
1. Position a vertical plane mirror and hold a book upright in front of it, with the book's front cover or spine text facing the camera.
2. Move the book slowly toward the mirror.
3. Move the book slowly back away from the mirror to its original position (or farther).
Observation of Experimental Phenomena
The mirror image of the book stays the same size as the real book at every distance; the image remains upright; the image's text/features appear mirrored left-right compared to the real book (e.g., letters read backward); the image appears exactly as far behind the mirror surface as the book is in front of it, so the image moves inward/outward in matching step with the book's motion.
Summary of Experimental Principles
A plane mirror forms a virtual image of the same size as the object, upright, and laterally inverted relative to the object, located as far behind the mirror as the object is in front of it — a direct consequence of the law of reflection (angle of incidence equals angle of reflection) applied to every point of the object.

Prompt Grounding rubric:
level_1: No book is visible, or no vertical mirror is visible, or the book's mirror image cannot be seen at all, or the book never moves at any point in the clip.
level_2: Both a book and a mirror appear, but one is not clearly identifiable (e.g., the mirror looks like a picture frame with no reflection, or the book is too blurred or occluded to make out as a book); or the book and its reflection are not both visible together in the same shot; or the camera angle changes so much that book and reflection are not comparable.
level_3: A book stands upright in front of a vertical plane mirror; the book's reflection is clearly visible in the mirror at the same time as the book itself; the book moves toward the mirror and then away from it, with both movements happening in view of a fixed camera.
level_4: Everything required for score 3 holds, and additionally: the book stays upright (not tilted or rotated) throughout its motion; the mirror stays flat, still, and undistorted; the camera framing keeps both the book and its full reflection in view without cropping either one; no hand, prop, or text overlay blocks the book or its reflection during the movements.
level_5: Everything required for score 4 holds, and additionally: the book's front cover or spine (with visible text or a distinct pattern) faces the camera throughout, making its orientation and any mirrored features easy to compare against the reflection; the book moves smoothly toward the mirror, pauses, then moves smoothly back, without stopping partway in a way that looks like an edit cut; the camera position, zoom, and angle stay fixed the entire time.

Scientific and Causal Correctness rubric:
level_1: The mirror image is not present, or it appears while the book itself does not, or the image shows an entirely different object than the book, or the image's size visibly grows and shrinks in a way that does not track the book's own motion at all.
level_2: The image is present but scientifically wrong in an obvious way: the image is clearly a different size than the book at any given moment, or the image is upside down, or the image is not laterally reversed (e.g., text on the book's spine reads the same, not mirrored, in the reflection).
level_3: At every moment shown, the mirror image is the same size as the book (neither shrinking nor growing relative to it as the book moves); the image stays upright, matching the book's up-down orientation; the image is laterally reversed relative to the book (e.g., any visible text or asymmetric feature on the book appears mirror-flipped in the image).
level_4: Everything required for score 3 holds, and additionally: as the book moves closer to the mirror, the image appears to move an equal amount closer to the mirror from behind it, not staying fixed or moving toward/away from the camera independently; as the book moves back away, the image recedes behind the mirror by the same amount; the image never appears to sit in front of the mirror surface or float to the side of it.
level_5: Everything required for score 4 holds, and additionally: the image's apparent distance behind the mirror visibly matches the book's distance in front of the mirror at every point during the motion, not just at the start and end; the lateral reversal is consistently visible on the same feature (e.g., the same word or logo) throughout, not just momentarily; the image's size-to-book ratio stays visually constant across the whole range of motion, with no visible extra magnification or shrinkage as distance changes.

Spatiotemporal Consistency rubric:
level_1: The book or its mirror image vanishes and reappears without any visible motion; the mirror flickers, changes size, or changes tilt abruptly; the book's shape distorts or breaks apart in a way a solid book cannot; the mirror's reflection shows a background or surroundings that don't match what's directly visible around the book (e.g., a different wall, ceiling, or object behind it than the reflection shows); the image and the book move independently with no visible correspondence at all.
level_2: The book's motion contains a visible jump: it appears at a new distance from the mirror without a visible path getting there; the mirror image lags noticeably behind the book's motion or leads it; the background behind the book or mirror shifts on its own even though the camera does not move; the book's or image's edges flicker or warp briefly during the motion.
level_3: The book's motion toward and away from the mirror is continuous and visibly smooth; the book itself keeps a fixed rigid shape and orientation throughout (aside from its overall motion); the mirror surface stays flat and stable; the image in the mirror moves in visible step with the book's own motion, growing or shrinking on-screen only to the extent the book itself does due to distance from camera.
level_4: Everything required for score 3 holds, and additionally: the book's speed of motion looks natural, without sudden bursts or freezes; the image tracks the book's motion with no visible delay or lead at any point; the book and mirror never clip through each other or overlap in an impossible way; the reflection stays fully confined within the mirror's frame, never spilling outside its edges.
level_5: Everything required for score 4 holds, and additionally: the book's approach to and retreat from the mirror plays out as one continuous motion without any visible cut or reset; the mirror frame and the wall or background around it stay rigid and undistorted throughout; the book and its image stay correctly aligned (same relative height, same tilt) at every moment, with no drifting apart or misalignment as the book moves.