The SI (International System) unit for Planck’s constant is approximately equal to 6.626176 x 10^-34 joule-seconds, whereas in the small-unit metric or centimeter-gram-second (cgs) system it is thought to be approximately equal to 6.626176 x 10^-27 erg-seconds.

Suppose that E is the energy contained in a photon and it is directly proportional to the frequency f of that electromagnetic wave, then according to the given equation:

Eµf

Or

E = hf

In terms of SI units, E is measured in joules and f (frequency) is measured in hertz, then:

E = (6.626176 × 10^-34) f

And hence,