[[quantum mechanics]]
denoted as $h$, equal to 6.62607015 × 10⁻³⁴ joule-seconds (J·s)

reduced plancks constant is $\hbar$, which is equal to $\frac{h}{2\pi}\approx 1.054571817 \times 10^{-34}$

used to relate a photons frequency to energy via $E=hf$