Domain: Natural Science — Physics
Target concept: The heating process of an incandescent lamp filament from a dark red glow to incandescence

Video generation prompt: A transparent old-fashioned incandescent light bulb is placed in a dimly lit room, connected to an adjustable power supply, whose power is gradually increased, causing the tungsten filament to gradually heat up.

Evaluation guide:
Target concept: Blackbody thermal radiation from resistively heated tungsten, governed by Wien’s displacement law and Stefan-Boltzmann law. Minimum mechanistic assumptions: (i) tungsten has positive temperature coefficient of resistance; (ii) electrical power input → thermal energy → electromagnetic emission; (iii) human vision perceives wavelength shifts as predictable color progression (red → orange → yellow-white) under fixed viewing conditions. Phased storyline: [0s] Cold filament (black, metallic); [2s] Onset of dark red (long-wavelength visible threshold); [4s] Saturated cherry red (uniform, medium luminance); [6s] Orange dominance (shorter λ, higher T); [8s] Yellow-white incandescence (broad-spectrum, high luminance); [10s] Stable warm white glow. Visibility constraints: Must be filmed frontally in dim room (≤10 lux) with no competing light sources; filament must remain in sharp focus throughout; color must be captured without auto-white-balance distortion. A rater verifies the color progression simply by watching whether the filament's glow visibly moves in order through black, dark red, orange, and yellow-white, without skipping a stage or reversing color at any point.

Manual:
I. Basic Demonstration Information
Demonstration Title: Incandescent Filament Thermal Glow Progression (Dark Red → Incandescence) Demonstration
Subject: Natural Science - Physics - Thermal Radiation & Electrical Resistance
Demonstration Purpose: To visually demonstrate the blackbody radiation behavior of a tungsten filament as it heats from ambient temperature to incandescence under controlled electrical power; to establish the causal link between resistive heating, temperature rise, and visible spectral emission; and to train visual recognition of thermal color progression as a diagnostic feature of temperature.

II. Demonstration Carrier/Equipment
Core Carrier: Transparent vintage incandescent bulb (E27 base, clear glass envelope, visible coiled tungsten filament, no halogen fill or coating)
Auxiliary Equipment: Dimly lit room (ambient illuminance ≤10 lux, no direct light on bulb), adjustable AC/DC power supply (0–120 V, with visible voltage dial or digital readout), insulated connecting wires, stable mounting stand (non-reflective matte black base).

III. Demonstration Content Description
Layout: Mount bulb vertically on stand at eye level; position power supply in same frame, visibly wired to bulb terminals; ensure unobstructed frontal view of filament coil.
State Control: Begin with power at 0 V (filament black, cold); gradually increase voltage over 8–10 s (0→5→15→30→60→90→110 V) while maintaining steady camera focus on filament.
Comparison Baseline: No reference objects — rely solely on intrinsic filament color/brightness evolution as self-referential thermal scale.

IV. Observation of Core Phenomena
Stage 1 (0–2 s): Filament completely black, no emission; surface texture sharp, metallic gray under ambient light.
Stage 2 (2–4 s): First visible emission — localized, low-luminance dark red glow (dull brick-red), confined to thickest filament segments; no orange/yellow present.
Stage 3 (4–6 s): Uniform cherry-red glow across entire coil; brightness increases noticeably; red is saturated, not pink or brown.
Stage 4 (6–8 s): Transition to orange-red → pure orange; glow fills coil volume; distinct warm hue, no blue/green contamination.
Stage 5 (8–10 s): Bright yellow-orange → warm white incandescence; high luminance, full-coil emission; filament retains crisp coil geometry (no sag/melting); color matches standard 2700K tungsten spectrum.
Characteristic Stability: Color progression is monotonic, irreversible, and intensity-correlated; no flicker, pulsing, or color reversal.

V. Summary of Key Knowledge Points and Principles
Core Concept Definition: Incandescence is visible light emission from a hot object due to thermal agitation; tungsten filament resistance increases with temperature, converting electrical energy into heat and then blackbody radiation.
Physics Principle: Wien’s Displacement Law (λ_max ∝ 1/T) explains color shift: ~1200 nm (IR) → 700 nm (red) → 600 nm (orange) → 550 nm (yellow) → 500 nm (white-yellow) as T rises from ~500 K to ~2500 K.
Causal Chain: Voltage ↑ → Current ↑ (Ohm’s Law, R rising) → Power dissipation (I²R) ↑ → Temperature ↑ → Spectral peak shifts ↑ → Visible emission onset → Color progression → Incandescence.
VI. Demonstration Precautions
- Use only vintage bulbs (not halogen/LED); verify transparency and coil visibility before demo.
- Avoid overvoltage (>120 V) to prevent filament burnout mid-demonstration.
- Maintain dim ambient light: no windows, lamps, or reflections on glass — ensures filament glow is the sole light source in frame.
- Record at ≥30 fps with manual white balance locked to ~2700K to preserve authentic color progression.
- Keep exposure fixed; auto-exposure will suppress early red stages.

Prompt Grounding rubric:
level_1: No incandescent bulb visible; no dimly lit room setting; no adjustable power supply shown; no visible filament or heating progression; scene is unrelated (e.g., LED lamp, daylight room, disconnected wire).
level_2: A bulb is present but opaque/LED/frosted; room is brightly lit; power supply is absent or non-adjustable (e.g., fixed battery); filament is invisible or static black; only 1–2 non-core elements align (e.g., bulb shape + wires), but core causal setup (dim room + adjustable power + visible tungsten filament) is missing.
level_3: Transparent old-fashioned incandescent bulb is visible and centered; room has reduced ambient light (but not clearly dim); adjustable power supply is shown (e.g., dial or slider), but filament remains cold/black for >3s without any glow; sequence starts correctly but fails to show *progression*: dark red → orange → yellow-white transition is absent or skipped.
level_4: All core physical elements present and correctly identified: transparent glass bulb, dim ambient lighting (no competing light sources), visible coiled tungsten filament, adjustable power supply (e.g., variable transformer or lab bench supply with voltage display), and *sequential onset* of glow: filament begins black, then shows faint dark red glow (~500°C), followed by brighter cherry-red (~700°C); minor defects: slight overexposure in later frames, or brief flicker obscuring one transition stage.
level_5: Perfect prompt grounding: (i) transparent vintage incandescent bulb (clear glass, visible tungsten coil, no coating/frosting); (ii) dimly lit room (low ambient illumination, shadows preserved, no glare/reflections on bulb surface); (iii) adjustable power supply visibly connected via insulated wires (dial/slider clearly turning or voltage readout increasing steadily); (iv) filament transitions *continuously and visibly* from black → dark red (dull, localized glow) → cherry red (brighter, wider emission) → orange-yellow (intense, full-coil luminance), all within natural color gamut and correct spectral order; no extraneous objects, labels, or distortions.

Scientific and Causal Correctness rubric:
level_1: Filament glows white instantly at full brightness; emits blue/purple light or greenish tint; changes color backward (e.g., white → red); no thermal progression logic; no causal link between power adjustment and glow; sound or motion contradicts physics (e.g., filament vibrating violently or cracking).
level_2: Glow appears without power increase (e.g., bulb already glowing at start); color jumps skip expected thermal stages (e.g., black → orange, omitting red); filament color violates blackbody radiation (e.g., magenta or cyan hues); power supply shows no change while glow intensifies; no temporal correlation between dial movement and brightness/color shift.
level_3: Filament heats and brightens sequentially, but colors are desaturated or inaccurate (e.g., red appears pink, yellow appears pale cream); temperature progression is roughly ordered (dark red → orange → yellow-white) but lacks clear visual distinction between stages; power adjustment is visible but timing misaligned (e.g., dial turns *after* glow change); minor causal disconnects (e.g., brightness increases before dial moves).
level_4: Color progression matches blackbody radiation expectations: dark red (~600–800 K) → cherry red (~900–1000 K) → orange (~1100–1300 K) → yellow-white (~1500–2000 K); brightness increases monotonically with power; dial movement precedes each visible glow transition by ≤0.5s; no non-physical artifacts (e.g., flicker, pulsing, or an abrupt jump straight from one hue to a distant one without passing through the intermediate color); filament remains structurally intact and stable, with no melting, sagging, or arcing.
level_5: Scientifically precise causal chain: (i) power supply voltage/current increases *first* (visible dial turn or numeric rise); (ii) filament resistance rises gradually (implied by stable coil geometry); (iii) thermal emission follows Planck’s law: spectral peak shifts from IR → deep red → orange → yellow-white with increasing intensity and chromatic saturation; (iv) no perceptible lag or overshoot: each stage emerges smoothly and persistently; (v) no violation of thermodynamics (e.g., no cooling phase, no spontaneous dimming); (vi) the final glow reads by eye as the warm yellow-white typical of a household tungsten filament at full brightness, never a cool white or blue-tinged white.

Spatiotemporal Consistency rubric:
level_1: The glass bulb visibly appears or disappears between frames, the coiled tungsten filament warps or stretches into an unnatural shape, or the power supply and bulb look disconnected or placed in different rooms; the filament's color jumps directly from black to white within a single frame with no dark-red or orange stage in between; the video freezes, stutters, or drops frames for more than a second at a time.
level_2: The connecting wires visibly change length or route between frames without cause; the bulb rotates or shifts sideways on its stand with no hand or mechanical action to explain it; a shadow near the bulb's base swaps to the opposite side of the frame partway through, inconsistent with a single fixed light source; two or more full stages of the glow sequence (e.g., dark red straight to yellow-white, skipping orange) are visibly skipped; the filament begins glowing before the power dial or voltage readout shows any increase.
level_3: The bulb stays fixed on its stand, the wires stay taut and connected, and the room background stays static; the filament's coiled shape shows a small amount of flicker or wobble in its outline that a close viewer could notice, without disrupting the overall coil form; the glow sequence is continuous but paced unevenly: for example the dark-red stage drags on far longer than the orange stage, or the reverse; the power dial's turning and the filament's brightening are only loosely matched in timing.
level_4: The bulb remains rigidly mounted with no rotation or drift; the connecting wires keep the same angle and tension throughout; any shadow cast by the bulb's socket or base on the stand keeps the same position and softness as the filament brightens; the coiled filament's shape stays intact with no sagging or melting; the glow moves smoothly and continuously through black, dark red, orange, and yellow-white with no doubled or skipped frames; the power dial's advance and the brightening of the glow track each other closely throughout the clip.
level_5: The bulb, socket, and connecting wires stay in exactly the same position and orientation for the entire clip, and any shadow near the bulb's base never shifts position or softness; within the 10-second clip, the glow moves through black, dark red, cherry red, orange, and yellow-white to a stable warm white in that correct order without skipping or reversing any stage; the power dial's advance and the filament's brightening/color change stay tightly matched in timing throughout; the filament's glowing edges stay crisp with no flicker, ghosting, or blurring as the color changes.