Physical constants

• Can Planck’s Constant Be Derived From Maxwell’s Equations?
  Maxwell’s equations predict classical electromagnetic waves, not Planck’s constant; quantum theory supplies the action scale needed to describe photon energies.
• What Is Planck’s Constant, Simply Explained?
  Planck’s constant sets the scale of quantum effects and relates a photon’s energy to its frequency through the equation E = hf.
• Can the Accuracy of Planck’s Constant Be Increased?
  Planck’s constant has an exact numerical value in the SI since 2019; experiments can improve its practical realization, not its defined value.