The photo cell works on the principle of the

Analysis

This question tests your understanding of Photoelectric Effect, a fundamental topic in Modern Physics. You are asked to identify the physical principle that allows a photocell (or photoelectric cell) to function.

Concept Explanation

A photocell is a device that converts light energy into electrical energy. It operates based on the Photoelectric Effect.

The photoelectric effect occurs when light (electromagnetic radiation) of a sufficiently high frequency strikes the surface of a metal. This interaction causes the metal to eject electrons from its surface. These ejected electrons are called photoelectrons. When these electrons flow through a circuit, they create an electric current.

• Key takeaway: The process involves light (incident radiation) hitting a surface and causing the release (emission) of electrons.

Step-by-Step Solution

1. Evaluate Option A: A Voltaic cell (or electrochemical cell) produces electricity through chemical reactions, not light. This is incorrect.
2. Evaluate Option B: This describes the photoelectric effect perfectly—incident radiation (light) causes the emission of electrons from a material. This is the correct principle.
3. Evaluate Option C: Protons are located in the nucleus of an atom and are not emitted during the photoelectric effect. This is incorrect.
4. Evaluate Option D: A photographic plate is used to record images through chemical changes caused by light, not to generate electrical current via electron emission. This is incorrect.

Conclusion

The photocell functions because incident light radiation provides enough energy to overcome the work function of the metal surface, resulting in the emission of electrons.

Exam Tip

Whenever you see "Photo" in Physics, think Light. Whenever you see "Electric," think Electrons. Therefore, "Photoelectric" simply means using light to move electrons!