Work functions for metals A and B are 2 eV and 4 eV respectively. Which metal has a lower threshold wavelength and why ?

Explanation

To determine which metal has a lower threshold wavelength based on their work functions, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Work Function**: The work function (φ) of a metal is the minimum energy required to remove an electron from the surface of that metal. It is given in electron volts (eV).

2. **Identify the Work Functions**: From the question, we have:
- Work function of Metal A (φ_A) = 2 eV
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