Get all the Optoelectronics devices MCQ which have already been asked in previous Engineering service Examinations (ESE) papers or this may come in upcoming exams also. So we have arranged almost all previous papers’ MCQs with answers and explanations given here. We will also cover the Special Diodes MCQs also.
Optoelectronics devices MCQs
1. LASER emission from Ruby crystal is because of transition
- (a) from the conduction band to the valance band of Al2O3
- (b) from the conduction band to one of the levels due to Cr ions.
- (c) between energy levels introduced by Cr ions
- (d) between one of the levels due to Cr ion and valance band Al2O3
2. The most suitable material for making an LDR (Light dependent Resistor) is a semiconductor material having
- (a) E_g >> h\nu
- (b) E_g > h\nu
- (c) E_g = h\nu
- (d)E_g << h\nu
3. An LED made using GaAs emits radiation in
- (a) Visible region
- (b) Ultraviolet region
- (c) Infrared region
- (d) Microwave frequency region
4. The Light Emitting Diode (LED) emits light of a particular color because
(a) It is fabricated from a fluorescent material
(b) the transition between energy levels of the carriers takes place while crossing the p-n junction
(c) the heat generated in the diode is converted into light
(d) the band gap of the semiconductor material used in the fabrication of the diode is equal to the energy hv of the light photon
5. The Gunn diode is made of
- (a) Silicon
- (b) germanium
- (c) Gallium Arsenide
- (d) Selenium
6. In an optoelectronic communication system, the system component in which free electrons are involved in its operation is
(a) Laser
(b) Optical Fiber
(c) Photo Detector
(d) Coupling device employed with the optical fiber
7. Which one of the following statement is correct? A tunnel diode is always biased
(a) by a d.c. source
(b) in the middle of its negative resistance region
(c) in the positive resistance region nearest to zero
(d) in the reverse direction
8. In which one of the following, two optical polarisers, one in from and the other in back are needed?
- (a) LED
- (b) LCD
- (c) LDR
- (d) LSI
9. A tunnel diode is
- (a) High resistivity p-n junction diode
- (b) A slow switching device
- (c) An amplifying device
- (d) A very heavily doped p-n junction diode
10. A hetero structure LASER is better than a diode LASER (injection LASER) because of its
- (a) Low cost
- (b) Long wavelength emission
- (c) Low threshold current
- (d) Non-linear operation
11. Which one of the following is an example of electroluminescent devices?
- (a) Liquid crystal display and photodiode
- (b) Liquid crystal display and phototransistor
- (c) Electroluminescent panel
- (d) Light emitting diode and phototransistor
12. Which of of the following is not LED material?
- (a) GaAs
- (b) GaP
- (c) SiC
- (d) SiO2
13.LED is a
- (a) p-n diode
- (b) Thermistor
- (c) Gate
- (d) Transistor
14. the I-V characteristics of a tunnel diode exhibits
- (a) current-controlled negative resistance
- (b) voltage-controlled negative resistance
- (c) temperature-controlled positive resistance
- (d)current-controlled positive resistance
15. The relative values of the forward conduction voltage for a p-n junction diode, a red LED and a Schottky barrier diode are
- (a) Schottky voltage drop > p-n junction diode drop > red LED drop
- (b) red LED drop > p-n junction diode > Schottky diode
- (c) p-n junction diode > Schottky voltage drop > red LED drop
- (d) Schottky voltage drop > red LED drop > p-n junction diode drop
16. The efficiency of an LED for generating light id directly proportional to the
- (a) applied voltage
- (b) current injected
- (c) temperature
- (d) level of doping
17. A tunnel diode is a p-n junction in which
- (a) n-region is degenerately doped
- (b) p-region is degenerately doped
- (c) either n or p-region is degenerately doped
- (d) both n and p-regions are degenerately doped
18. which is the diode used for measuring light intensity?
- (a) junction diode
- (b) varactor diode
- (c) tunnel diode
- (d) photodiode
19. the wavelength beyond which photo electric emission cannot take place is called
- (a) long wavelength
- (b) optical wavelength
- (c) photoelectric wavelength
- (d) critical wavelength
20. the basic material for the fabrication of an LED is
- (a) gallium arsenide
- (b) gallium arsenide phosphide
- (c) indium antimonide
- (d) indium antimonide phosphide
21. swept-out voltage in pin diode happens when pin diode is
- (a) forward biased and thickness of the depletion layer decreased till the l-region becomes free of mobile carriers
- (b) reverse biased and the thickness of the depletion layer increases till the region becomes free of mobile carriers
- (c) forward biased and the thickness of the depletion layer increases till the region becomes free of mobile carriers
- (D) reverse biased and the thickness of the depletion layer decreases till the I region becomes free of mobile carriers
23. A tunnel diode is best suited for
- (a) very low frequencies
- (b) 50Hz
- (c) 100kHz
- (d) microwave frequencie
23. maximum energy of electrons liberated photoelectrically is
- (a) proprortional tolight intensity and independent of frequncy of light
- (b) independent of light intencity and varies linearly with frequency of the light
- (c) proptional to both, light intencity and freqency of the light
- (D) independent of light intrnsity and inversely proprtional to frequncy of the light
24. necessary condition for photoelectric emission is
- (a) hv>e
- (b) hv>mc
- (c) hv>e
- (d) hv >1/2mc
24. in photoconductive cell,the resistance of the semiconductor material varies with the intensity of incident light
- (a) directly
- (b) inversely
- (c) exponentially
- (d) logarithmically
25. which of the following materials is used in light emitting diodes?
- (a) gallium arsenide sulphate
- (b) gallium arsenide phosphide
- (c) gallium chromate sulphate
- (d) gallium phosphide sulphate
