Planck constant

The Planck constant hh is a constant originally introduced in Planck's attempt to solve black body radiation. In SI units it is approximately equal to

h=6.626×10−34 J⋅sh=6.626\times10^{-34}\ \text{J}\cdot\text{s}

The reduced Planck constant is also used:

ℏ=h2π=1.054572×10−34 J⋅s\hbar=\frac{h}{2\pi}=1.054572\times10^{-34}\ \text{J}\cdot\text{s}

Besides the extremely small value, the Planck constant has the dimensions of an angular momentum. This is important because it is the fundamental unit of Spin for subatomic particles.