Luminous efficacy of 540 THz radiation = 683 lm·W⁻¹
- Symbol
- Kcd
- Value
- 683
- Unit
- lm·W⁻¹
- Uncertainty
- exact (by definition)
- Copy-ready
683
Defines the candela, tying photometric units to radiant power.
NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.
The seven SI defining constants
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UsePhysics. "Luminous efficacy of 540 THz radiation — 683 lm·W⁻¹." UsePhysics.com. https://usephysics.com/reference/luminous-efficacy. Value from the 2022 CODATA adjustment (NIST). Accessed [date].