Optoelectronics Overview
26 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of a Light Emitting Device?

  • To liberate bound electrons within semiconductor materials
  • To sense changes in light intensity
  • To convert electromagnetic energy into electric current
  • To produce electromagnetic radiation using voltage and current (correct)

    • What characterizes Light Detecting Devices?

  • They convert received electromagnetic energy into electric current or voltage. (correct)
  • They emit light to provide illumination.
  • They operate by generating photons.
  • They are less efficient than incandescent lamps.

    • How do humans perceive color in terms of photons?

  • Using a mechanism involving electric current
  • Through the different wavelengths of photons
  • By the inherent property of photons
  • By interpreting the frequency of photons as color (correct)

    • What is a characteristic of a photon with a longer wavelength?

    <p>It corresponds to a lower frequency and less energy.</p> Signup and view all the answers

    Which type of lamp is known for its very hot bulbs and brilliant light?

    <p>Halogen lamp</p> Signup and view all the answers

    What is the approximate lifespan of an incandescent lamp?

    <p>1,000 hours</p> Signup and view all the answers

    What is a distinctive feature of fluorescent lamps?

    <p>They use a mercury vapor-filled tube coated with a fluorescing material.</p> Signup and view all the answers

    What distinguishes an LED from other types of lamps?

    <p>It converts electric current into visible light energy more efficiently.</p> Signup and view all the answers

    What is the transfer gain's typical value in terms of output voltage to input current?

    <p>200 mV/mA</p> Signup and view all the answers

    Which of the following is NOT an advantage of fiber optic cables over copper wires?

    <p>More susceptibility to interference</p> Signup and view all the answers

    What material primarily makes up the core of a fiber optic cable?

    <p>Glass</p> Signup and view all the answers

    What happens to a light ray when the angle of incidence is less than the critical angle?

    <p>The light ray is refracted into the cladding</p> Signup and view all the answers

    What is the function of the cladding in a fiber optic cable?

    <p>To serve as a reflective surface</p> Signup and view all the answers

    What determines the intensity of light emitted by an LED?

    <p>The forward current through the LED</p> Signup and view all the answers

    What is the primary advantage of using a photodarlington over a regular phototransistor?

    <p>It has a higher current gain</p> Signup and view all the answers

    What is the main function of an opto isolator?

    <p>To provide electrical isolation between two circuits</p> Signup and view all the answers

    What does the isolation voltage represent in an opto isolator?

    <p>The maximum voltage without dielectric breakdown</p> Signup and view all the answers

    When measuring the DC Transfer Ratio, what does a value of 100 percent indicate for a phototransistor output?

    <p>The output current is equal to the input current</p> Signup and view all the answers

    What is the primary energy conversion mechanism of a photodiode?

    <p>It converts light energy directly into electric current.</p> Signup and view all the answers

    What is a common application for laser diodes?

    <p>Bar code scanners.</p> Signup and view all the answers

    Which statement about LED lamps is true?

    <p>They use light-emitting diodes to produce light.</p> Signup and view all the answers

    How does a photoresistor behave in darkness?

    <p>It has high resistance.</p> Signup and view all the answers

    What is a major advantage of solar cells compared to standard photodiodes?

    <p>They have exceptionally large areas for better sensitivity.</p> Signup and view all the answers

    What type of light do phototransistors respond best to?

    <p>Light within a certain range of wavelengths.</p> Signup and view all the answers

    The efficiency of LED lamps compared to incandescent lamps is characterized by which trait?

    <p>Long lifespan and high energy efficiency.</p> Signup and view all the answers

    What is the primary function of a solar cell?

    <p>To convert light into electrical energy.</p> Signup and view all the answers

    Study Notes

    Optoelectronics

    • The study and application of electronic devices and systems that source, detect, and control light. Focuses on light emitting and detecting devices.
    • Two main types: Light Emitting Devices (LEDs) and Light Detecting Devices.

    Light Emitting Devices (LEDs)

    • Use voltage and current to produce electromagnetic radiation (light).
    • Common uses include illumination and indicator lights.

    Light Detecting Devices

    • Convert electromagnetic energy into electric current or voltage.
    • Used for light sensing and communication (e.g., darkness-activated switches, remote controls).
    • Operate by using photons to liberate bound electrons in semiconductor materials.

    Photons

    • Fundamental units of electromagnetic radiation.
    • Human eyes are sensitive to optical electromagnetic radiation (EMR), interpreted as different colors based on frequency (not inherent photon property).
    • Longer wavelength (lower frequency) photons have less energy than shorter wavelength (higher frequency) photons.

    LED Devices: Types and Characteristics

    • Lamps: Convert electric current into visible light.
      • Incandescent Lamps: Tungsten filament, short lifespan (~1000 hours).
      • Halogen Lamps: Advanced incandescent, brighter, hotter bulbs, stronger glass, less efficient than LEDs.
      • Fluorescent Lamps: Mercury vapor-filled tube, 10,000-hour lifespan.
      • LED Lamps: Use light-emitting diodes (LEDs), significantly longer lifespan (20,000-30,000 hours), much more efficient than incandescent and most fluorescent lamps.
    • Light Emitting Diodes (LEDs): Semiconductor diodes emitting incoherent, narrow-spectrum light when forward-biased. Applications include communications, remote controls, displays, and solid-state lighting.
    • Laser Diodes: Semiconductor laser devices similar to LEDs, emitting light through optical amplification based on stimulated emission. Much faster response than LEDs. Applications include laser pointers, barcode scanners, CD players, and molecular identification.

    Light Detecting Devices: Types and Characteristics

    • Photoresistors (Light Dependent Resistors): Light-variable resistors; high resistance in darkness, low resistance in light. Applications include LDR switches.
    • Photodiodes: Two-lead semiconductor devices converting light energy directly into electric current; function as photodetectors.
    • Solar Cells: Large-area photodiodes, highly sensitive to light, producing higher voltage and current than photodiodes. Used in solar panels and light detectors.
    • Phototransistors: Transistors where base current is produced by light striking the photosensitive base region. Sensitivity to a specific light wavelength range.
    • Photodarlingtons: Phototransistor and BJT in Darlington configuration; higher current gain and light sensitivity than phototransistors.
    • Optical Couplers (Opto Isolators): Electrically isolate two circuits using an LED and a phototransistor in a light-tight enclosure.

    Optical Coupler Characteristics

    • Isolation Voltage: Maximum voltage between input and output terminals before dielectric breakdown (typically ~7500 V ac peak).
    • DC Transfer Ratio: Ratio of output current to input current (%). Ranges from 2-100% for phototransistors; 50-500% for photodarlingtons.
    • LED Trigger Current: Current needed to trigger the thyristor output (mA range, for LASCR and phototriac outputs).
    • Transfer Gain: Ratio of output voltage to input current for AC linear couplers (e.g., 200 mV/mA).

    Fiber Optics

    • Transmit information using light pulses through fiber optic cables (diameter ~100 microns).
    • Advantages over copper wires: faster speed, higher signal capacity, longer transmission distances without amplification, less susceptibility to interference, more economical maintenance.

    Fiber Optic Cable Operation and Components

    • Light "bounces" along the fiber, reflected by the cladding.
    • Components:
      • Core: The glass fiber itself.
      • Cladding: Surrounds the core; provides a reflective surface.
      • Outer Coating/Jacket: Provides protection.
    • Angle of Incidence: Angle at which light strikes the surface.
    • Critical Angle: Angle determining reflection or refraction; light reflects back into the core if the angle of incidence exceeds the critical angle.
    • Scattering Loss: Energy loss due to refraction when angle of incidence is less than critical angle.
    • Absorption Loss: Energy loss due to interaction of photons with core molecules.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Optoelectronics Notes Module 4 PDF

    Description

    Explore the fascinating field of optoelectronics, focusing on the study and application of electronic devices that source, detect, and control light. Delve into the differences between Light Emitting Devices (LEDs) and Light Detecting Devices, and learn about the role of photons in these processes.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser