Question Discussion & Solution

CONCEPT:​

• Power of Lens: The inverse of the focal length is known as the power of the lens.
  • It shows the bending strength for the light ray of the lens.

\(P = \frac{1}{f}\)

where P is the power of the lens and f is the focal length of the lens.

• The unit of power of a lens is Dioptre when the focal length of the lens is taken in meter (m).
• The focal length of the convex lens (converging) is positive and that of the concave lens (diverging) is negative. 

CALCULATION:

Given that lens is diverging. so focal length is negative.

f = -5 cm = -0.05 m

Power of lens \(P = \frac{1}{f} =\frac{1}{-0.05} = -20 D\)

P = -20 D

So the correct answer is option 2.

The correct answer is Copper and Tin.
Key Points

• Bronze
  • Bronze is an alloy traditionally composed of copper and tin.
  • Bronze is of exceptional historical interest and still finds wide applications.
  • It was made before 3000 BC, though its use in artifacts did not become common until much later.
  • The proportions of copper and tin varied widely (from 67 to 95 percent copper in surviving artifacts), but, by the Middle Ages in Europe, certain proportions were known to yield specific properties.
  • An alloy described in an 11th-century Greek manuscript in the library of St. Mark’s, Venice, cites a proportion of one pound copper to two ounces of tin (8 to 1), approximately that used for bronze gunmetal in later times.
  • Some modern bronzes contain no tin at all, substituting other metals such as aluminum, manganese, and even zinc.

Additional Information

• Copper and Silver
  • The best-known copper-silver alloy is sterling, which is 92.5 percent silver and 7.5 percent copper.
  • In England sterling, silver is traditionally identified by the hallmark of a lion passant.
  • Coin silver is an alloy of 90 percent silver and 10 percent copper.
  • For jewelry and ornaments, 85–90 percent silver (and the balance copper) is frequently used.
  • Dental alloys of 60–70 percent silver, 18–25 percent tin, 2–14 percent copper, and 0.5–2 percent zinc are amalgamated with varying quantities of mercury to form the filling materials for cavities in teeth.
• Copper and zinc
  • Brass is an alloy of copper and zinc, of historical and enduring importance because of its hardness and workability.
  • The earliest brass was called calamine brass, which dates to Neolithic times.
  • It was probably made by the reduction of mixtures of zinc ores and copper ores.
  • In ancient documents, such as the Bible, the term brass is often used to denote bronze, the alloy of copper with tin.
• Copper and Lead
  • Leaded bronzes contain from 4 to 25 percent lead plus additions of copper and tin, and some copper-lead bearing alloys contain up to 40 percent lead.
  • All these bearing alloys are sufficiently soft so that lubrication failure does not result in damage to the bearing.
  • Lead-based bearing alloys are also known as lead-based babbitt metals or white metals.
  • These are usually antimonial lead with widely variable additions of tin or copper (or both) and arsenic to increase strength.
  • One such alloy is commonly used for railroad-car journal bearings, contains 86 percent lead, 9 percent antimony, and 5 percent tin.
  • Many alloys of lead and alkaline-earth metals, such as calcium and sodium, also are widely used as bearing materials.

The correct answer is Afforestation.

• Afforestation is not a cause of soil erosion.

Key Points

• Afforestation is planting trees on an area of land in order to form a forest.
• Removal of the top layer of soil when it is exposed to wind and rain is easily blown or washed away. This condition is known as soil erosion.
  • Basically, the soil cover is removed by two powerful agents– (i) Running water, (ii) Wind.
• Deforestation, overgrazing, floods, Landslides and heavy rainfall have led to soil erosion.

The correct answer is DBMS.

Key Points

• DBMS is NOT antivirus software.
• A database is a collection of related data that depicts a real-world situation. A database system is made to be developed and filled with information for a certain activity.
• A database management system (DBMS) is software that stores and retrieves data for users while taking proper security precautions. It is made up of a collection of applications that manipulate the database.
• The DBMS accepts an application's request for data and informs the operating system to give the requested data.
• A database management system (DBMS) aids users and other third-party applications in storing and retrieving data in huge systems.
• Users can design their own databases using a database management system (DBMS).
• The term "DBMS" refers to the database user as well as other application applications. It serves as a link between the data and the software program.

• McAfee Corp. is a San Jose, California-based global computer security software corporation.
• Avast Antivirus is a cross-platform internet security suite created by Avast for Microsoft Windows, macOS, Android, and iOS.
• Avira Operations GmbH & Co. KG is a German multinational computer security software firm best known for its Avira Free Security antivirus software. 

The correct answer is EEPROM.

Key Points

• Flash memory is a non-volatile computer storage chip,
• It is made up of EEPROM.
• EEPROM is the acronym of electrically erasable programmable read-only memory,
• EEPROM is a Programmable ROM that can be erased and reprogrammed using an electrical charge.
• It was first was developed by George Perlegos.
• It allows the user to update the computer BIOS without having to open the computer or remove any chips.
• It organized as arrays of floating-gate transistors.
• USB flash drive, Memory cards are the examples of flash memory storage.
• BIOS is stored in Flash memory chip.

Additional Information

• RDRAM is the acronym of Rambus Dynamic Random Access Memory.
  • It is a video RAM.
• MROM is the acronym of Mask ROM.
  • It is produced by arranging transistors before the semiconductor manufacturing process actually begins.
• SRAM is the acronym of Static random-access memory
  • It uses latching circuitry (flip-flop) to store each bit.
• PROM is the acronym of Programmable Read-Only Memory.
  • It can be modified only once by a user.