# Quantum Efficiency , Responsivity and Long – Wavelength Cut-Off MCQ’s

This set of Optical Communication Multiple Choice Questions & Answers (MCQs) focuses on “Quantum Efficiency , Responsivity and Long – Wavelength Cut-Off”.

1. In photo detectors, energy of incident photons must be ________________ band gap energy.
a) Lesser than
b) Greater than
c) Same as
d) Negligible

2. GaAs has band gap energy of 1.93 eV at 300 K. Determine wavelength above which material will cease to operate.
a) 2.431*10-5
b) 6.424*10-7
c) 6.023*103
d) 7.234*10-7

3. The fraction of incident photons generated by photodiode of electrons generated collected at detector is known as ___________________
a) Quantum efficiency
b) Absorption coefficient
c) Responsivity
d) Anger recombination

4. The long cutoff wavelength of GaAs is 0.923 μm. Determine bandgap energy.
a) 1.478*10-7
b) 4.265*10-14
c) 2.784*10-9
d) 2.152*10-19

5. Determine quantum efficiency if incident photons on photodiodes is 4*1011 and electrons collected at terminals is 1.5*1011?
a) 50%
b) 37.5%
c) 25%
d) 30%

6. The quantum efficiency of photodiode is 40% with wavelength of 0.90*10-6. Determine the responsivity of photodiodes.
a) 0.20
b) 0.52
c) 0.29
d) 0.55

7. Quantum efficiency is a function of photon wavelength.
a) True
b) False

8. A photodiode has quantum efficiency of 45% and incident photons are 3*1011. Determine electrons collected at terminals of device.
a) 2.456*109
b) 1.35*1011
c) 5.245*10-7
d) 4.21*10-3

9. The Responsivity of photodiode is 0.294 AW-1at wavelength of 0.90 μm. Determine quantum efficiency.
a) 0.405
b) 0.914
c) 0.654
d) 0.249

10. Determine wavelength at which photodiode is operating if energy of photons is 1.9*10-19J?
a) 2.33
b) 1.48
c) 1.04
d) 3.91

11. Determine Responsivity of photodiode having o/p power of 3.55 μm and photo current of 2.9 μm.
a) 0.451
b) 0.367
c) 0.982
d) 0.816

12. Determine wavelength of photodiode having quantum efficiency of 40% and Responsivity of 0.304 AW-1.
a) 0.87 μm
b) 0.91 μm
c) 0.88 μm
d) 0.94 μm

13. Determine incident optical power on a photodiode if it has photocurrent of 2.1 μA and responsivity of 0.55 A/W.
a) 4.15
b) 1.75
c) 3.81
d) 8.47

14. Determine the energy of photons incident on a photodiode if it operates at a wavelength of 1.36 μm.
a) 1.22*10-34J
b) 1.46*10-19J
c) 6.45*10-34J
d) 3.12*109J

15. If a photodiode requires incident optical power of 0.70 A/W. Determine photocurrent.
a) 1.482
b) 2.457
c) 4.124
d) 3.199