The phenomenon of photoelectric effect was first explained by

Options

A. Hallwach
B. Einstein
C. Planck
D. Bohr

Answer

**Step-by-Step Solution:**

1. **Understanding the Photoelectric Effect**: The photoelectric effect is a phenomenon where electrons are emitted from a material (usually a metal) when it is exposed to light (or electromagnetic radiation) of sufficient energy.

2. **Historical Context**: The photoelectric effect was a significant discovery in physics that contributed to the understanding of light and its particle-like properties.

3. **Key Contributor**: The first person to explain the photoelectric effect was Albert Einstein. His explanation was pivotal in the development of quantum theory.

4. **Nobel Prize Recognition**: Albert Einstein was awarded the Nobel Prize in Physics in 1921 for his explanation of the photoelectric effect, which provided evidence for the quantization of light.

5. **Work Function Concept**: In his explanation, Einstein introduced the concept of the "work function," which is the minimum energy required to remove an electron from the surface of a metal. For electrons to be emitted, the energy of the incoming photons must be greater than this work function.

6. **Conclusion**: Therefore, the correct answer to the question of who first explained the phenomenon of the photoelectric effect is Albert Einstein.

**Final Answer**: Albert Einstein

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