Albert Einstein was awarded Nobel Prize for his work on

Options

A. Special theory of relativity
B. General theory of relativity
C. Photoelectric effect
D. Mass-energy equivalence

Answer

**Step-by-Step Solution:**

1. **Understanding the Nobel Prize Awarded to Einstein**: Albert Einstein was awarded the Nobel Prize in Physics in 1921. It is important to identify the specific contribution for which he was honored.

2. **Identifying the Contribution**: The Nobel Prize was awarded to Einstein primarily for his explanation of the photoelectric effect. This effect describes how light can cause the emission of electrons from a material.

3. **Explaining the Photoelectric Effect**: The photoelectric effect occurs when photons (light particles) strike a metal surface. If the energy of the incoming photons is sufficient, they can transfer energy to electrons in the metal, allowing these electrons to escape from the surface.

4. **Work Function Concept**: For an electron to be emitted from the metal, the incoming photon must have energy greater than a certain threshold known as the work function (φ). This is the minimum energy required to remove an electron from the surface of the metal.

5. **Einstein's Equation**: Einstein formulated the relationship between the energy of the incoming photons and the kinetic energy of the emitted electrons. The equation can be expressed as:
\[ E_{photon} = \phi + KE \]
where \(E_{photon}\) is the energy of the incoming photon, \(\phi\) is the work function, and \(KE\) is the kinetic energy of the emitted electron.

6. **Conclusion**: Einstein's work on the photoelectric effect not only provided a deeper understanding of light and its interaction with matter but also laid the groundwork for the development of quantum mechanics. This significant contribution is why he was awarded the Nobel Prize.

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