Physical Sciences – DBE 2025 MayJune – Question 1.10 – Matter and Materials

The Question

Details

💡 Hint

What is the core interaction between light and electrons in the photoelectric effect? Does the electron gain or lose energy, and what is the outcome?

📝 Solution Steps

1. 1. Recall the fundamental definition of the photoelectric effect.
2. 2. Evaluate each option to see if it aligns with this definition.
3. 3. Identify the option that correctly describes the absorption of photon energy by an electron leading to its ejection from a metal surface.

📚 Explanation

The photoelectric effect is a quantum phenomenon where electrons are ejected from the surface of a metal when it is exposed to electromagnetic radiation (like light) of a sufficiently high frequency. This occurs because an electron absorbs the energy of a single photon, and if this energy is greater than the work function of the metal, the electron is ejected.
* A) ‘An electron absorbs the energy of a photon and emits light’ describes fluorescence or phosphorescence, not the photoelectric effect.
* B) ‘An electron emits a photon when it collides with another electron’ describes an inelastic collision, not the photoelectric effect.
* C) ‘An electron absorbs the energy of a photon and is ejected from the surface of a metal’ is the correct definition of the photoelectric effect.
* D) ‘A photon is emitted when an electron moves from a lower energy level to a higher energy level’ is incorrect; a photon is emitted when an electron moves from a higher to a lower energy level.

✅ Answer

C

⚠️ Common Mistakes

• Confusing the photoelectric effect with other light-matter interactions (e.g., light emission, electron excitation).
• Misunderstanding the role of photons in the process.