Part – B (General Studies) NDA/NA SOLVED PAPER 2018 (I) (51 to 100)

Periscope is an optical instrument which is based on the phenomenon of reflection of light. Light is reflected from the first mirror into the second one at 45° angle which is then reflected to the eye of the viewer.

20-20,000 Hz, human ear can respond to minute pressure variations in air. The audible frequency range to which ears can respond is 20-20,000 Hz. The sound frequency beyond this limit may damage ear drums and cause hearing disabilities in humans.

The accidental touch of Nettle Leaves create a burning sensation. This is due to the methanoic acid secreted by them.
It is a Herbaceous plant that grows in the wild. The leaf of the dock plant, which often grows beside the nettle, is the traditional remedy for it.

Tooth pastes are derived from different variety of components namely abrasives, flouride and detergents. Abrasives includes particles of calcium hydrogen phosphates, aluminium hydroxide, etc.
Tooth pastes are basic in nature and prevents tooth decay by neutralising the excess of acid. They can neither be acidic nor normal.

The amount of H⁺ ions produced depends upon the strength of an acid which further depends on the corresponding pH values. Relation between pH and concentration of H⁺ ions is given by

As the pH increases, the acidic nature decreases and thus the amount of H⁺ ions. The order of pH values for the above given options are as follows:
Gastric Juice (1.3 − 3.0) < Lemon Juice
(2.2-2.4) < Milk of Magnesia (10.5) < Sodium hydroxide (≈ 14)
Thus, Gastric juice gives the highest amount of H⁺ ions.

Brine is an aqueous solution of sodium chloride (NaCl). Electrolysis of brine produces Sodium Hydroxide (NaOH), Chlorine (Cl₂) and Hydrogen (H₂). This forms the basis of the chlor-alkali industry.

Bleaching powder (CaOCl₂) is produced by the action of chlorine on dry slaked lime [Ca(OH)₂]. The following are the uses of bleaching powder:
(i) It is used for bleaching purposes in textile industries, paper industry and in laundry.
(ii) It is also used as a disinfectant for water to make it free of germs.
(iii) It is used as an oxidising agent in many chemical industries.
Thus among the given, option (a) is incorrect.

AIDS is caused by Human Immunodeficiency Virus (HIV). It belongs to family retroviridae and genus lentivirus.
HIV genome consists of two identical copies of the SSRNA genome, reverse transcriptase enzyme and other proteins to code for viral proteins that are essential during its replication. All these components are: enclosed within the core of viral particle.

Prokaryotic cells are simple and primitive type of cells e.g. bacteria, methanogens, blue-green algae, etc. These cell do not contain membrane bound nucleus and other cellular organelles like other than mitochondria, prokaryotes also lack.
Mitochondria is a double membraned organelle, which is responsible for the production of ATP molecules. It is only found in eukaryotic cells.