The correct answer is option 2 - Albert Einstein.

The phenomenon of photoelectric effect is the emission of electrons from a material when it is exposed to light or other forms of electromagnetic radiation. Albert Einstein explained this phenomenon in 1905, earning him the Nobel Prize in Physics in 1921.

Einstein proposed that light is made up of discrete packets of energy called photons. When light of sufficient energy, or frequency, strikes a material, it can transfer its energy to an electron in the material. This transfer of energy can cause the electron to be ejected from the material, resulting in the photoelectric effect.

Einstein`s explanation of the photoelectric effect laid the foundation for the concept of the dual nature of light, which states that light can exhibit both wave-like and particle-like properties. His work also contributed to the development of quantum mechanics, revolutionizing our understanding of the behavior of particles at the atomic and subatomic level.

In summary, Albert Einstein is credited with explaining the phenomenon of photoelectric effect by proposing the concept of photons and their interaction with electrons in materials.