Question

In the formula $E = hf$ what does $f$ stand for?

Answer 1

The given equation represents the energy of a particular radiation of a certain frequency. In the given equation, E stands for energy, h represents Planck’s constant and f stands for frequency. This equation is useful to determine the energy or frequency when another term is given.

Complete answer:
Photo electric effect is defined as the ejection of electrons from a metal surface, when a light energy is incident on the surface of the metal. Caesium is the most electropositive element in the periodic table. All the alkali earth metals show the photoelectric effect.
Einstein defined a quantum of electromagnetic energy, in which the energy of a photon can be given by the equation of $E = hf$ where quantum is a massless packet of light energy. It does not have any mass and does not occupy any space. Thus, quanta is a form of radiation which is nothing but light energy.
Einstein explained the phenomenon of photoelectric effect and gave the equation $E = hf$ in which E stands for energy of the photon, h stands for Planck’s constant and f stands for frequency. Thus, E gives the information of energy associated with a certain frequency $f$ .
Thus, in the given equation f stands for frequency.

Note:
The given equation leads to the basic steps to evaluate quantum mechanics. From this equation it was clear that the energy of a particle which is a photon is directly proportional to the frequency of a photon. Planck’s constant corresponds to the energy of one quantum.