Answer: (A)

Explanation:

• SONAR is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.
• Dedicated sonars can be fitted to ships and submarines for underwater communication. Sonars which act as beacons are fitted to aircraft to allow their location in the event of a crash in the sea. Sound waves travel differently through fish than through water because a fish’s air-filled swim bladder has a different density than seawater. This density difference allows the detection of schools of fish by using reflected sound. Acoustic technology is especially well suited for underwater applications since sound travels farther and faster underwater than in air.

Hence, both statement-I and statement-II are correct and statement II is the correct explanation for statement-I.

Answer: (D)

Explanation:

• Neutrinos are the information bearers of the universe — which are almost never lost in their path. India’s effort in studying neutrinos at INO may help us unravel the deepest mystery of the universe — why there is more matter than antimatter in the universe.
• Neutrinos are the least harmful of all elementary particles, as they almost never react with solid bodies. Also, people tend to confuse the “neutrino” for the “neutron”. This has also led to the confusion that neutrinos can be weaponised, which is far from the truth. They are not used to trigger fission reactions, but are instead produced as a result of the reactions. Neutrinos have mass and as shown recently, they change their masses too. The neutrino is so named because it is electrically neutral. Hence, all statements are incorrect.

Answer: (A)

Explanation:

• The Treaty on the Prohibition of Nuclear Weapons (TPNW), or the Nuclear Weapon Ban Treaty, is the first legally binding international agreement to comprehensively prohibit nuclear weapons, with the goal of leading towards their total elimination. Hence, statement 1 is correct.
• It was adopted on 7 July 2017, opened for signature on 20 September 2017, and entered into force on 22 January 2021. Hence, statement 2 is incorrect.
• For those nations that are party to it, the treaty prohibits the development, testing, production, stockpiling, stationing, transfer, use and threat of use of nuclear weapons, as well as assistance and encouragement to the prohibited activities. For nuclear armed states joining the treaty, it provides for a time-bound framework for negotiations leading to the verified and irreversible elimination of its nuclear weapons programme. Hence, statement 3 is incorrect.

Answer: (A)

Explanation: A bacteriophage is a type of virus that infects bacteria. In fact, the word “bacteriophage” literally means “bacteria eater,” because bacteriophages destroy their host cells. All bacteriophages are composed of a nucleic acid molecule that is surrounded by a protein structure. In other words, they are comprised of a protein capsule around an RNA or DNA genome. Hence, statement 2 is incorrect.

Answer: (C)

Explanation: Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice. It is nearly transparent. It is the basic structural element of many other allotropes of carbon, such as graphite, charcoal, carbon nanotubes and fullerenes. Its thin composition and high conductivity means it is used in applications ranging from miniaturised electronics to biomedical devices. These properties also enable thinner wire connections; providing extensive benefits for computers, solar panels, batteries, sensors and other devices. The one-atom-thick sheets of carbon conduct electrons better than silicon and have been made into fast, low-power transistors. Researchers have measured the intrinsic strength of graphene, and they’ve confirmed it to be the strongest material ever tested. Hence, only statement 4 is incorrect.