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

p -n photodiode is a semiconductor diode that produces a significant current when illuminated.  It is reversed biased but is operated below the breakdown voltage. Energy of radiation = Band gap energy That is hv = 2.0 eVor  v=2.0×1.6×10-196.6×10-34≈5×1014Hz