20+ Top Photodetectors MCQs with Answers
Which type of photodetector is based on the principle of internal photoemission?
a) Photodiode
b) Phototransistor
c) Photoconductor
d) Schottky barrier photodetector
Answer: d
Hint: Internal photoemission occurs at the Schottky barrier.
In a photodiode, the photocurrent is generated when:
a) Light illuminates the depletion region
b) Light passes through the substrate
c) Light induces electron-hole recombination
d) Light is absorbed by the substrate
Answer: a
Hint: Photocurrent is generated in the depletion region of the photodiode.
A phototransistor is a type of photodetector that operates as a:
a) Reverse-biased diode
b) Bipolar junction transistor
c) Schottky barrier diode
d) Varactor diode
Answer: b
Hint: Phototransistors use a bipolar junction transistor configuration.
The responsivity of a photodetector is a measure of its:
a) Quantum efficiency
b) Response time
c) Gain
d) Threshold voltage
Answer: a
Hint: Responsivity relates the output current to the incident optical power.
In which type of photodetector does the photocurrent increase linearly with the incident light intensity?
a) Photodiode
b) Phototransistor
c) Photoconductor
d) Avalanche photodiode
Answer: c
Hint: Photoconductors have a linear response to light intensity.
Which photodetector is based on the principle of carrier multiplication through impact ionization?
a) Photodiode
b) Phototransistor
c) Photoconductor
d) Avalanche photodiode
Answer: d
Hint: Avalanche photodiodes exhibit carrier multiplication through impact ionization.
The spectral response of a photodetector refers to its sensitivity to different:
a) Incident angles of light
b) Wavelengths of light
c) Polarizations of light
d) Refractive indices of materials
Answer: b
Hint: Spectral response is about sensitivity to different wavelengths.
Photoconductors are semiconductor devices that exhibit an increase in:
a) Resistivity when exposed to light
b) Conductivity when exposed to light
c) Capacitance when exposed to light
d) Inductance when exposed to light
Answer: b
Hint: Photoconductors become more conductive when illuminated.
The mechanism responsible for the increased conductivity in photoconductors is:
a) Impact ionization
b) Electron-hole recombination
c) Carrier multiplication
d) Photon absorption
Answer: d
Hint: Photoconductivity arises due to photon absorption by the semiconductor material.
Compared to a dark condition, the dark current in a photoconductor is:
a) Higher
b) Lower
c) Unchanged
d) Zero
Answer: b
Hint: Dark current decreases in the presence of light in photoconductors.
Photoconductors are commonly used in applications requiring:
a) High-speed data transmission
b) High-power amplification
c) Light emission
d) Energy harvesting
Answer: a
Hint: Photoconductors are used in high-speed data transmission systems.
Which of the following materials is commonly used in photoconductor devices?
a) Silicon
b) Copper
c) Aluminum
d) Glass
Answer: a
Hint: Silicon is a widely used material in photoconductors.
In a photoconductor, the absorption of photons generates:
a) Electron-hole pairs
b) Electric fields
c) Magnetic fields
d) Protons
Answer: a
Hint: Incident photons create electron-hole pairs in the photoconductor.
The process by which photoconductors return to their original state after the light source is removed is called:
a) Recombination
b) Excitation
c) Relaxation
d) Oscillation
Answer: c
Hint: After the light source is removed, photoconductors relax to their initial state.
Photodiodes are semiconductor devices that convert light into:
a) Heat
b) Electricity
c) Magnetism
d) Sound
Answer: b
Hint: Photodiodes convert incident light energy into electrical current.
Which of the following is a reverse-biased photodiode mode of operation?
a) Photovoltaic
b) Photoconductive
c) Phototransistor
d) Photoemissive
Answer: b
Hint: In photoconductive mode, the photodiode is reverse-biased.
The photocurrent in a photodiode is directly proportional to the:
a) Light intensity
b) Applied voltage
c) Temperature
d) Photodiode area
Answer: a
Hint: Photocurrent increases with increasing light intensity.
Which material is commonly used in the construction of photodiodes?
a) Copper
b) Aluminum
c) Silicon
d) Glass
Answer: c
Hint: Silicon is a widely used material for photodiodes.
The response time of a photodiode refers to its speed of:
a) Light emission
b) Signal amplification
c) Photon absorption
d) Current generation
Answer: d
Hint: Response time is the speed of generating electrical current in response to light.
The depletion region of a photodiode is responsible for:
a) Absorbing light
b) Generating electrons and holes
c) Providing electrical contacts
d) Reducing reverse current
Answer: a
Hint: The depletion region absorbs incident photons and creates electron-hole pairs.
A phototransistor is a semiconductor device that amplifies current in response to:
a) Heat
b) Light
c) Magnetic fields
d) Mechanical pressure
Answer: b
Hint: Phototransistors amplify current based on incident light.
The base current in a phototransistor is controlled by the:
a) Collector’s current
b) Incident light intensity
c) Applied voltage
d) Emitter’s current
Answer: b
Hint: Incident light intensity affects the base current.
Phototransistors are often used for:
a) Generating heat
b) Emitting light
c) Sensing light
d) Amplifying magnetic fields
Answer: c
Hint: Phototransistors are used for light-sensing applications.
In a phototransistor, light is incident on the:
a) Emitter region
b) Collector region
c) Base region
d) Depletion region
Answer: c
Hint: Incident light strikes the base region of the phototransistor.
The output current of a phototransistor is controlled by the:
a) Base current
b) Incident light intensity
c) Collector’s current
d) Emitter’s current
Answer: c
Hint: The output current is determined by the collector current.
Which type of phototransistor has an intrinsic base region?
a) NPN
b) PNP
c) Darlington
d) Avalanche
Answer: a
Hint: In NPN phototransistors, the base region is intrinsic.
What is the primary function of a Charge-Coupled Device (CCD)?
a) Amplify current
b) Generate heat
c) Convert light into electrical charge
d) Emit light
Answer: c
Hint: CCDs convert incident light into electrical charge.
In a CCD, the electrical charge generated by incident light is stored in:
a) Photodiodes
b) Capacitors
c) Resistors
d) Inductors
Answer: b
Hint: CCDs use capacitors to store electrical charge.
Which of the following is a common application of CCDs?
a) Generating sound waves
b) Recording magnetic fields
c) Capturing images in digital cameras
d) Transmitting radio signals
Answer: c
Hint: CCDs are widely used in digital cameras for image capture.
The transfer of charge within a CCD is achieved using:
a) Electromagnetic fields
b) Electric currents
c) Mechanical force
d) Shift registers
Answer: d
Hint: CCDs utilize shift registers to transfer charges.
Which property of CCDs allows them to capture high-resolution images?
a) Low sensitivity to light
b) High-speed response
c) Large pixel size
d) High charge storage capacity
Answer: d
Hint: CCDs with high charge storage capacity can capture high-resolution images.
In a CCD, the charge transfer is performed by:
a) Photodiodes
b) Phototransistors
c) Capacitors
d) Clock signals
Answer: d
Hint: Clock signals facilitate the charge transfer within a CCD.
Solar cells convert _______ into electrical energy.
a) Mechanical energy
b) Thermal energy
c) Solar radiation
d) Magnetic energy
Answer: c
Hint: Solar cells harness energy from sunlight.
The material commonly used in the fabrication of solar cells is:
a) Silicon
b) Aluminum
c) Copper
d) Gold
Answer: a
Hint: Silicon is a widely used material in solar cell technology.
The process by which photons are absorbed in a solar cell and generate electron-hole pairs is called:
a) Reflection
b) Absorption
c) Emission
d) Diffusion
Answer: b
Hint: Absorption of photons leads to the generation of electron-hole pairs.
The majority of commercially available solar cells are based on which technology?
a) Amorphous silicon
b) Organic materials
c) Multi-junction cells
d) Single-crystalline silicon
Answer: d
Hint: Single-crystalline silicon is the most commonly used technology for commercial solar cells.
The bandgap of a semiconductor material used in solar cells should be:
a) Very narrow
b) Very wide
c) Approximately 1 eV
d) Equal to 0 eV
Answer: b
Hint: A wide bandgap is preferred to efficiently absorb solar radiation.
Solar cells work on the principle of:
a) Photodiode effect
b) Piezoelectric effect
c) Photoelectric effect
d) Electromagnetic induction
Answer: c
Hint: Solar cells operate based on the photoelectric effect.
What happens to the excess energy of a photon with energy greater than the bandgap of the semiconductor in a solar cell?
a) It is lost as heat
b) It is reflected back
c) It is converted into more than one electron-hole pair
d) It is converted into a single electron-hole pair
Answer: a
Hint: Excess energy of high-energy photons is dissipated as heat.
The efficiency of a solar cell is defined as:
a) The percentage of absorbed sunlight
b) The percentage of reflected sunlight
c) The percentage of converted sunlight into electrical energy
d) The percentage of transmitted sunlight
Answer: c
Hint: Efficiency measures the percentage of sunlight converted into electrical energy.
Which type of solar cell is known for its flexibility and lightweight properties?
a) Crystalline silicon solar cell
b) Amorphous silicon solar cell
c) Multi-junction solar cell
d) Concentrated solar cell
Answer: b
Hint: Amorphous silicon solar cells offer flexibility and lightweight characteristics.
The open-circuit voltage of a solar cell is the voltage across its terminals when:
a) It is not exposed to sunlight
b) Its terminals are short-circuited
c) It is connected to an external load
d) It is exposed to maximum sunlight
Answer: c
Hint: The open-circuit voltage is measured when the solar cell is connected to an external load
What is the purpose of the output amplifier in a CCD?
a) Convert charge to light
b) Amplify the electrical charge
c) Generate clock signals
d) Store data in a memory buffer
Answer: b
Hint: The output amplifier amplifies the electrical charge before reading out the data.
CCDs are commonly used in which field for scientific imaging and research?
a) Astronomy
b) Agriculture
c) Sports
d) Fashion
Answer: a
Hint: CCDs are extensively used in astronomy for capturing images of celestial objects.
What is the typical arrangement of pixels in a CCD image sensor?
a) Square grid
b) Hexagonal grid
c) Rectangular grid
d) Random arrangement
Answer: c
Hint: Pixels in a CCD image sensor are arranged in a rectangular grid.
In a CCD, the readout process involves:
a) Converting charge to light
b) Converting light to charge
c) Transferring charge to capacitors
d) Transferring charge to an external memory
Answer: d
Hint: During readout, the charge is transferred to external memory for further processing
Phototransistors can be used in applications that require:
a) Low gain
b) High voltage
c) High-speed response
d) Low sensitivity to light
Answer: c
Hint: Phototransistors offer high-speed response for fast applications.
When light falls on the base region of a phototransistor, it causes:
a) Reduction in base current
b) Reduction in collector current
c) Increase in base current
d) No change in collector’s current
Answer: c
Hint: Incident light increases the base current in a phototransistor.
Phototransistors are commonly made from which semiconductor material?
a) Aluminum
b) Copper
c) Silicon
d) Glass
Answer: c
Hint: Silicon is commonly used for phototransistors.
A phototransistor operates in which mode of operation?
a) Forward bias
b) Reverse bias
c) Cut-off
d) Active
Answer: d
Hint: Phototransistors operate in the active mode to amplify current based on light intensity
In a photodiode, reverse bias is used to:
a) Increase dark current
b) Reduce responsivity
c) Enhance photon absorption
d) Decrease photocurrent
Answer: c
Hint: Reverse bias widens the depletion region and improves photon absorption.
The spectral responsivity of a photodiode describes its sensitivity to different:
a) Light intensities
b) Wavelengths of light
c) Electrical currents
d) Operating temperatures
Answer: b
Hint: Spectral responsivity indicates the sensitivity to specific wavelengths.
Which of the following factors can limit the bandwidth of a photodiode?
a) Photon absorption
b) Depletion region width
c) Speed of electron-hole recombination
d) Forward biasing
Answer: c
Hint: The recombination speed can limit the photodiode’s bandwidth.
Avalanche photodiodes are capable of:
a) Emitting light
b) Multiplying photocurrent
c) Generating heat
d) Absorbing magnetic fields
Answer: b
Hint: Avalanche photodiodes use avalanche multiplication to increase the photocurrent
The resistance of a photoconductor decreases as the intensity of incident light:
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: a
Hint: More light causes a decrease in photoconductor resistance.
Photoconductor materials are chosen based on their ability to absorb light in specific:
a) Colors
b) Angles
c) Polarizations
d) Wavelengths
Answer: d
Hint: The choice of photoconductor depends on the required wavelength sensitivity.
Which of the following factors can limit the performance of photoconductors?
a) Photon absorption
b) High resistivity
c) Electron-hole recombination
d) Light intensity
Answer: c
Hint: Recombination processes can limit photoconductor performance
Photodetectors are used to convert:
a) Electrical signals to optical signals
b) Mechanical signals to electrical signals
c) Optical signals to electrical signals
d) Magnetic signals to mechanical signals
Answer: c
Hint: Photodetectors convert optical signals to electrical signals.
In which type of photodetector is the output current inversely proportional to the light intensity?
a) Photodiode
b) Phototransistor
c) Photoconductor
d) Photovoltaic cell
Answer: d
Hint: Photovoltaic cells have a current output inversely proportional to light intensity.
Photodetectors used in fiber optic communication systems are typically based on:
a) Photoconductors
b) Photodiodes
c) Phototransistors
d) Photovoltaic cells
Answer: b
Hint: Photodiodes are commonly used in fiber optic communication systems
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