Two metals a and b have work function 5 eV and 7 eV , respectively . Which metal has a lower threshold wavelength ?

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 Work Function and Threshold Wavelength**:
The work function (Φ) of a metal is the minimum energy required to remove an electron from the surface of that metal. The threshold wavelength (λ) is related to the work function by the equation:
\[
\Phi = \frac{hc}{\lambda}
...