Picture description::
International System of Units (SI) have been defined by physical constants since May 20, 2019, as following:
- the caesium hyperfine frequency (ΔνCs) is 9 192 631 770 Hz;
- the speed of light in vacuum (c) is 299 792 458 m/s;
- the Planck constant (h) is 6.626 070 15× 10-34 J s;
- the elementary charge (e) is 1.602 176 634 × 10-19 C;
- the Boltzmann constant (k) is 1.380 649 × 10-23 J/K;
- the Avogadro constant (NA) is 6.022 140 76 × 1023 mol-1;
- the luminous efficacy of a defined visible radiation (Kcd) is 683 lm/W.
Posted Date: 2019/05