Explain the following sonars and photovoltaic cells

8 a] Explain the following sonars and photovoltaic cells


Sonar, short for “sound navigation and ranging,” is a technology that uses sound waves to navigate, communicate, and detect objects underwater. It operates on a principle like echolocation, widely used in marine and underwater applications, including navigation, communication, mapping, and detecting underwater objects and obstacles.

  1. Active Sonar: The system generates its sound waves and listens for the echoes. This is used for underwater mapping, navigation, and detecting submarines or other vehicles.
  2. Passive Sonar: Only listen for sound waves produced by other sources, such as engines or propellers of ships and submarines. Used for detecting & tracking underwater vessels without revealing the sonar system’s presence.
  3. Side-Scan Sonar: Provides detailed images of the seafloor by emitting sound waves to the sides and capturing the echoes. Used for underwater mapping & searching for objects like shipwrecks or submerged debris.
  4. Multibeam Sonar: It emits multiple sound beams simultaneously in a fan-like pattern, allowing for rapid and detailed mapping of the seafloor or underwater structures


  1. Sound Wave Generation: A sonar system emits sound waves into the water, typically in short pulses of sound. These sound waves are often at frequencies beyond the range of human hearing and can travel long distances underwater.
  2. Propagation and Reflection: The emitted sound waves travel through the water and interact underwater with various objects, surfaces, and boundaries. When the sound waves encounter an object, they are partially reflected toward the sonar system.
  3. Echo Detection and Timing: The sonar system has a receiver that detects the echoes produced by the reflected sound waves. By measuring the time, it takes for the echoes to return to the system, the distance to the object can be calculated using the speed of sound in water.
  4. Image or Data Creation: The information gathered from the echoes is processed by a computer to create visual representations or data displays. In some cases, sonar systems can generate detailed images of underwater structures, terrain, or objects based on the echoes and their timing.

Photovoltaic Cells (Solar Cells):

Photovoltaic cells, also known as solar cells, are semiconductor devices that convert sunlight (photons) into electricity (voltage and current).Materials: Common materials used in photovoltaic cells include silicon (crystalline and amorphous), cadmium telluride, Quantum Dots, and organic polymers


  • Light Absorption: Photovoltaic cells have a semiconductor layer that absorbs photons from sunlight, exciting electrons.
  • Electron Movement: Excited electrons create an electric current when they move through the semiconductor material.
  • Generation of Electricity: The electric current generated is used as electrical power or stored in batteries for later use.
  • Efficiency: The efficiency of photovoltaic cells varies by material and technology. It’s typically in the range of 15% to 22% for commercial cells, with advanced designs achieving higher efficiencies.


  • Renewable and clean energy source.
  • Low environmental impact during operation.
  • Reduces dependence on fossil fuels.

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