The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480\text{ nm}$ is incident on it. The band gap in ($\text{eV}$) for the semiconductor is:

1. A
   $1.1\text{ eV}$
2. B
   $2.5\text{ eV}$
3. C
   $0.5\text{ eV}$
4. D
   $0.7\text{ eV}$