Input Physics Parameterilluminance
Physical Domain Reference
Direct sunlight: ~100,000 Lux. Office lighting: 300–500 Lux. Full moon night: 0.1–0.3 Lux.
Standardized Output
Calculated Result
46.4515fc
500 Lux (lm/m²) equals 46.4515 Foot-Candle (lm/ft²).
Physics Derivation Steps
Step 1: Compute normalized SI Base:
500 lx ➔ 5.0000e+2 SI
Step 2: Apply conversion factor or logarithmic transformation:
Result = 46.4515 fc
Full Multi-Unit Conversion Matrix for 500 lx4 Units Available
| Unit Name | Symbol | System Classification | Equivalent Quantity |
|---|---|---|---|
| Lux (lm/m²) | lx | SI Base | 500 |
| Foot-Candle (lm/ft²) Selected Target | fc | Imperial Architectural | 46.45152 |
| Phot (lm/cm²) | ph | CGS Photometric | 0.05 |
| Nox (Millilux) | nx | Low-Light / Military | 500000 |
Electromagnetism, Optics, Ionizing Radiation & Acoustics Engineering Manual
Rigorous definitions of illuminance vs luminance, magnetic flux density, radiobiological dosimetric equivalents, and logarithmic decibel scales.
1Photometry: Illuminance (Lux) vs Luminance (Nit)
In optical science, confusion frequently arises between illuminance and luminance:
- Illuminance (Lux = lm/m²): Quantifies the total luminous flux incident upon a given surface area. Measured by placing a light sensor on a desk or floor. 1 Foot-candle equals approximately 10.764 Lux.
- Luminance (Nit = cd/m²): Quantifies the luminous intensity emitted, transmitted, or reflected from a surface per unit projected area in a given direction. It describes perceived display brightness (e.g., iPhone outdoor peak brightness: 2,000 nits).
2Magnetic Flux Density (Tesla) vs Total Magnetic Flux (Weber)
The magnetic field vector B represents magnetic flux density, measured in Tesla (T ≡ 1 N/(A·m) = 1 Wb/m²) in SI and Gauss (G) in CGS units, where 1 Tesla = exactly 10,000 Gauss.
Integrating magnetic flux density over an area yields the total magnetic flux (Φ = ∫ B · dA), measured in Webers (Wb ≡ 1 V·s). According to Faraday's Law of Induction, a magnetic flux changing at the rate of 1 Weber per second through a closed coil loop induces an electromotive force (EMF) of exactly 1 Volt.
3Ionizing Radiation Dosimetry: Gray (Absorbed) vs Sievert (Biological)
Evaluating radioactive exposure mandates tracking two distinct dosimetric quantities:
Absorbed Dose (Gray, Gy):Physical radiation energy absorbed per unit mass of matter:
1 Gray ≡ 1 Joule / kg
1 rad = 0.01 Gray
Applicable to all ionizing materials.
1 Gray ≡ 1 Joule / kg
1 rad = 0.01 Gray
Applicable to all ionizing materials.
Equivalent Dose (Sievert, Sv):Biological radiation damage weighted by radiation type (Wr):
H = D × Wr (alpha particles have Wr = 20)
1 Sievert = 100 rem
Average annual natural background: ~2.4 mSv
H = D × Wr (alpha particles have Wr = 20)
1 Sievert = 100 rem
Average annual natural background: ~2.4 mSv
4Acoustic Decibel Scales & Psychoacoustic Loudness (Sones)
Human auditory perception spans an astronomical acoustic pressure range: from the threshold of hearing at 20 micropascals (0 dB SPL) to the threshold of physical pain at 200 Pascals (140 dB SPL)—a factor of ten million in linear pressure!
To compress this vast range, the logarithmic Sound Pressure Level (SPL) formula is employed:
L_p = 20 × log10(p / p0) [where p0 = 20 µPa = 2 × 10⁻⁵ Pa]
+3 dB SPL = Doubling of physical acoustic power
+10 dB SPL = Doubling of human-perceived psychological loudness (1 Sone = 40 phon)
+3 dB SPL = Doubling of physical acoustic power
+10 dB SPL = Doubling of human-perceived psychological loudness (1 Sone = 40 phon)