A p-n junction photodiode is fabricated from a semiconductor with a band gap of 4 10⁻¹⁹ J. It can detect a signal of wavelength [h = 6.6 10⁻³⁴ Js , C = 3 10^8 m/s ]

Step-by-step solution

For a photodiode to detect a signal, the energy of the incident photon must be greater than or equal to the band gap energy of the semiconductor. E E_g hc E_g hc E_g Substituting the given values: 6.6 10⁻³⁴ 3 10^8 4 10⁻¹⁹ 19.8 10⁻²⁶ 4 10⁻¹⁹ 4.95 10⁻⁷ m 4950 Among the given options, only 4000 is less than 4950 . Answer: 4000 Å