# Tag Info

Here's a very basic way to see this easily: This is Action, search for the "Abbreviated Action", and it has the SI unit of Joule-second. This is the equation that Planck (and later, Einstein) used: $$E=nhf$$ for $n=1,2,3...$ and $f$ in frequency, in unit of 1/second). This means that the Planck's constant has also an unit of Joule-second, therefore, you ...