Question Discussion & Solution

The correct answer is option 2 i.e C₄H_10.

Concept:

Hydrocarbons

• Compounds made of carbon and hydrogen atoms only are called hydrocarbons.
• Saturated hydrocarbons:
  • The hydrocarbons in which carbon atoms are singly bonded are called saturated hydrocarbons.
  • Saturated hydrocarbons are also called alkanes or paraffin.
    • The general formula of alkane– CnH2n+2.
• Unsaturated hydrocarbons:
  • The hydrocarbons in which carbon atoms are either doubly or triply bonded are called unsaturated hydrocarbons.
  • Doubly bonded (carbon atoms) hydrocarbons are called alkenes.
  • The general formula of alkene is CnH2n.

• The formula for alkane should be mentioned C_nH_2n+2

Explanation:

CONCEPT:

• Power is the ability to bend light and it is equal to the reciprocal of the focal length of the lens/mirror in meters.

Power (P) = 1/f

Where f is the focal length of the lens/mirror.

EXPLANATION:

As explained above, Dioptre is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres.

And since the S.I unit of the focal length is the meter (m).

So the S.I unit of power = 1/(SI unit of focal length) = m-1 = Dioptre (D).

1 m-1 = 1 D

Correct Option -2

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Binary semaphores are also known as Mutex locks, as they are locks that provide mutual exclusion.

Explanation:-

Binary semaphores:- This is also known as mutex lock. It can have only two values 0 and 1. Its value is initialized to 1. It is used to implement the solution of critical section problems with multiple processes.

 Important PointsCounting semaphores:- Its value can range over an unrestricted domain. It is used to control access to a resource that has multiple instances

Using mutex:- A mutex provides mutual exclusion, either producer or consumer can have the key (mutex) and proceed with their work. 

Shared variable:- A semaphore is a shared variable that is used to implement mutual exclusion between system processes.
 Additional InformationSemaphore used:- Semaphores are typically used in one of two ways: To control access to a shared device between task. A Printer is a good example. You don'twant 2 tasks sent to the printer at once, so you create a binary semaphore to control printer access.

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.