Question

In general, as the temperature increases, the electron work function of metal would

• A. Becomes zero at finite temperature
• B. Independent of temperature
• C. Decrease
• D. Increase

Answer 1

The Correct Option is C

We need to determine the general effect of increasing temperature on the electron work function of a metal.

1. Understanding the Work Function:
The work function of a metal is the minimum energy required to remove an electron from its surface to infinity. It is a material-specific property, typically denoted by \( \phi \), and depends on the electronic structure of the metal.

2. Temperature Dependence:
The work function is primarily determined by the metal's surface properties and its Fermi energy level, which are intrinsic characteristics. However, temperature can influence the work function indirectly:
- As temperature increases, thermal energy causes lattice vibrations (phonons) and can slightly alter the electronic energy levels and surface conditions.
- These effects may lead to a small decrease in the work function because thermal energy can assist in overcoming the potential barrier, effectively reducing the energy needed to eject an electron.
- Experimental studies show that for most metals, the work function decreases slightly with increasing temperature, often on the order of a few meV per 100 K, due to thermal expansion and changes in the surface dipole layer.

3. General Trend:
While the effect is small and varies by metal, the general trend is that the work function decreases as temperature increases, as thermal effects facilitate electron emission (e.g., in thermionic emission).

Final Answer:
In general, as the temperature increases, the electron work function of a metal would decrease.