Planck's constant relates the energy in one photon of electromagnetic radiation to the frequency of the radiation, varying:

directly

inversely

indirectly

randomly

Option (b) "inversely

"

Explanation:

The energy of a photon is given by :

Where

h is the Planck's constant

c is the speed of light

is the wavelength

Or it can be written as :

.....(1)

is the frequency.

Equation (1) can be rearranged as :

So, it is clear that Planck's constant relates the energy in one photon of electromagnetic radiation is inversely proportional to the frequency of the radiation. Hence, the correct option is (b) "inversely".