MHT CET202123 Sep 2021Morning ShiftPhysicsSemiconductorsActual
A p-n junction photodiode is fabricated from semiconductor with a band gap of 2.5 eV . It can detect a signal of wavelength [Planck's constant =6.6 10⁻³⁴ Js , c =3 10^8 ~m / s , e =1.6 10⁻ . ¹⁹ C ]
Options
- A6000 ~nm
- B6000 Å
- C5000 Å
- D4000 ~nm
Correct answer
C. 5000 Å
Step-by-step solution
The wavelength corresponding to 2.5 eV is given by Energy ( eV )= 12400 (Å) = 12400 2.5 =5000 Å To get detected, the signal should have energy greater than 2.5 eV or wavelength less than 5000 Å .