A p-n photodiode is made of a material with a band gap of 2.0eV. The minimum frequency of the radiation that can be absorbed by the material is nearly :

Question

$\begin {array} {1 1} (1)\;20 \times 10^{14}Hz & \quad (2)\;10 \times 10^{14}Hz \\ (3)\;5 \times 10^{14}Hz & \quad (4)\;1 \times 10^{14}Hz \end {array}$