Question

Work function of the metal is

• A. Maximum possible energy acquired by an electron
• B. Equal for all metals
• C. Minimum energy required by an electron to just eject from metal surface
• D. Maximum energy which is given to electron to move out of metal surface

Hint:

Think of the work function as the "entry fee" or "toll" an electron must pay to leave the metal "territory." Any extra energy provided by a photon above this "toll" becomes the kinetic energy of the electron.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
This question asks for the fundamental definition of the "work function" in the context of the photoelectric effect and solid-state physics.
Step 3: Detailed Explanation:
Electrons within a metal are held by the attractive forces of the atomic nuclei. To escape the surface of the metal, an electron must overcome a potential energy barrier.
The work function (\(\Phi_0\) or \(W\)) is defined as the minimum amount of energy that must be supplied to an electron to just enable it to escape from the surface of the metal with zero kinetic energy.
- It is a characteristic property of the metal; different metals have different work functions (e.g., Alkali metals have low work functions while transition metals like Platinum have high ones).
- If the incident photon energy is less than the work function, no photoemission occurs.
- Therefore, option (1) is wrong as it describes kinetic energy, option (2) is wrong because it's not universal, and option (4) is wrong because it's a minimum threshold, not a maximum limit.
Step 4: Final Answer:
The work function is the minimum energy required for an electron to just eject from the metal surface, which is option (3).