MCQs on Photodiode for NEET

The photodiode generates current when exposed to light. It can also be called a photodetector or photosensor. It works on the principle of the photoelectric effect. Photodiodes work in reverse biased mode. When the junction of the photodiode is illuminated, then the electric current starts flowing.

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Q1: Photodiode is used in the detection of

  1. Visible light
  2. Invisible light
  3. No light
  4. Both visible and invisible light

Answer: (d) Both visible and invisible light

Q2: In using a photodiode as a photodetector, it is invariably reverse biased

  1. The power consumption is much reduced compared to reverse biased condition
  2. Only when the photodiode is reverse biased the incident photons produce electron-hole pairs
  3. Only if the diode is reverse biased light variations can be converted into current variations
  4. When photons are incident on the diode, the fractional change in the reverse current is much greater than the fractional change in the forward current

Answer: (d) When photons are incident on the diode, the fractional change in the reverse current is much greater than the fractional change in the forward current.

Q3: The maximum wavelength of photons that can be detected by a photodiode made by a semiconductor of bandgap 2eV is about

  1. 620 nm
  2. 700 nm
  3. 740 nm
  4. 1240 nm

Answer: (a) 620 nm

Q4: The presence of dark current decreases the sensitivity of the photodiode to light

  1. True
  2. False

Answer: (a) True

Q5: Photodiodes operate by absorption of photons or charged particles and generate a flow of current in an external circuit,……….. to the incident power. The light is absorbed ……….with distance and is ………..to the absorption coefficient.

  1. Proportional, exponentially, proportional
  2. Proportional, logarithmically, inversely proportional
  3. Inversely proportional, exponentially, unrelated

Answer: (a) Proportional, exponentially, proportional

Q6: What is the reason phototransistor produces more current than a photodiode?

  1. A wider spectrum is accepted by the phototransistor than the photodiode
  2. The current produced by photons is amplified by the hfe of the transistor
  3. The phototransistor can heavily doped than the photodiode
  4. At low light conditions, a photodiode is used.

Answer: (c) The current produced by photons is amplified by the hfe of the transistor

Q7: In a photodiode, when there is no incident light, the reverse current is almost negligible and is called

  1. Zener current
  2. Dark current
  3. Photocurrent
  4. PIN current

Answer: (b) Dark current

Q8: Compared to a photo-diode, which of the listed advantages and disadvantages would be expected of a phototransistor

  1. Faster response and greater sensitivity
  2. Faster response and less sensitivity
  3. Slower response and greater sensitivity
  4. Slower response and less sensitivity

Answer: (c) Slower response and greater sensitivity

Q9: When a diode is forward biased, the recombination of free electron and holes produce

  1. Heat
  2. Light
  3. Radiation
  4. All the above

Answer: (d) All the above

Q10: The width of the depletion region is

  1. Directly proportional to the doping
  2. inversely proportional to the doping
  3. Independent of doping
  4. None of the above

Answer: (b) inversely proportional to the doping

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