Test: Science & Technology - 2 (March 10, 2021)


25 Questions MCQ Test UPSC CSE Prelims 2021 Mock Test Series | Test: Science & Technology - 2 (March 10, 2021)


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QUESTION: 1

The ceilings of cinema halls, conference halls and concert halls are generally curved in order to:

Solution:

Generally, the ceilings of concert halls, conference halls, and cinema halls are curved so that sound after reflection reaches all corners of the hall, as shown in the figure.

QUESTION: 2

Which of the following are the initiatives to promote digital payments in India?

  1. Mandatory facility for electronic modes of payment for businesses with turnover over rupees fifty crores.

  2. Waiver of Merchant Discount Rate (MDR) charges.

  3. Levying surcharge on cash withdrawals of one crore and above.

Select the correct answer using the code given below.

Solution:
  • Option 1 is correct: With effect from January 1, 2020, the Centre has made it mandatory for business entities having a turnover of over ₹50 crores to provide facilities for accepting payments via the prescribed electronic modes.

  • The Central Board of Direct Taxes (CBDT) has notified the modes of payment, in addition to the facility for other electronic modes, as:

    • Debit Card powered by RuPay

    • Unified Payments Interface (UPI) (BHIM-UPI)

    • Unified Payments Interface Quick Response Code (UPI QR Code) (BHIM-UPI QR Code).

  • Under the Payment and Settlement Systems Act, 2007, no charge, including Merchant Discount Rates (MDR), shall be levied by banks on payments made through prescribed electronic modes.

  • Option 2 is correct: For all the transactions less than Rs 2,000 in value, the consumer and the merchant will not suffer any additional burden in the form of MDR.

  • The government will bear the MDR charges on transactions up to Rs 2,000 to promote digital transactions.

  • Option 3 is correct: The government will charge a two percent tax if aggregate cash withdrawal from one or more accounts exceeds Rs 1 crore.

  • It will be a tax deduction at source (TDS) to discourage high-value withdrawals.

QUESTION: 3

Some of the mammals, like humans and whales, share similarities in the pattern of bones of forelimbs. But these bones perform different functions in these mammals. Which of the following correctly explains this type of evolution?

Solution:
  • Divergent evolution refers to the case where different organisms have the same ancestry (homologous) but they evolve differently, according to the needs of their environment. Hence option (b) is the correct answer.

  • An example of divergent evolution is the human arm, the whale’s fin, and the bat's wing. All three limbs perform different purposes, but all contain the same bones in different sizes and shapes because all three animals (human, whale, bat) evolved from a common ancestor whose legs contained those bones. For humans, upright walking on the ground required alterations in the foot for better speed and balance. The whale and bat modified the ancestral structure in response to environmental pressures of their own. These differing traits soon became characteristics that evolved to permit movement over the ground and in the water and air.

  • Convergent evolution is just opposite to the divergent evolution. It is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

  • Co-evolution is the situation where two types of organisms, in a symbiotic relationship, evolve simultaneously, so that they keep pace with one another.

QUESTION: 4

Which of the following applications/ phenomena are based on the Doppler effect?

  1. Echolocation by bats.

  2. Sonic boom

  3. Police radar for measuring the speed of vehicles

Select the correct answer using the code given below.

Solution:
  • All the options are correct.

  • Doppler Effect: The Doppler effect is a phenomenon observed whenever the source of waves is moving with respect to an observer. The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for the observer and the source are approaching and an apparent downward shift in frequency when the observer and the source are receding. The Doppler effect can be observed to occur with all types of waves - most notably water waves, sound waves, and light waves.

  • Examples: A police car or emergency vehicle was traveling towards you on the highway. As the car approached with its siren blasting, the pitch of the siren sound (a measure of the siren's frequency) was high; and then suddenly after the car passed by, the pitch of the siren sound was low. That was the Doppler effect - a shift in the apparent frequency for a sound wave produced by a moving source.

  • Applications of Doppler Effect:

    • Police radar to check the speed of vehicles on a highway.

    • To read weather events. In this case, the stationary transmitter is located in a weather station and the moving object being studied is a storm system.

    • Echocardiogram.

    • Sonic boom produced by the supersonic aircraft.

  • Echolocation by bats: To help them find their prey in the dark, most bat species have developed a remarkable navigation system called echolocation

QUESTION: 5

Which of the following is/are the applications of Mycorrhizal biotechnology - a result of symbiotic associations between plant roots and soil fungi?

  1. Rehabilitation of degraded land.

  2. To enable plants to resist droughts.

  3. To enable disease/pest resistance in plants.

Select the correct answer using the code given below.

Solution:
  • Mycorrhiza is symbiotic association between plant roots and certain soil fungi which play a key role in nutrient cycling in the ecosystem and also protect plants against environmental and cultural stress. Most of the major plant families are able to form mycorrhiza, the arbuscular mycorrhizal (AM) association being the most common mycorrhizal type involved in agricultural systems.

  • Mycorrhizal biotechnology has been used in rehabilitating degraded lands because mycorrhiza enables the plants to resist drought and increase the absorptive area. It also helps to tolerate extremes of pH which resists disease infestation.

  • Hence all the statements are correct.

QUESTION: 6

A concave lens is used for correction of which of the following eye defects?

  1. Myopia

  2. Hypermetropia

  3. Presbyopia

Select the correct answer using the code given below.

Solution:
  • Myopia or shortsightedness is an eye defect in which the person is unable to see far objects clearly. It occurs either due to the shifting of the retina or due to a decrease in the focal length of the lens. It can be corrected by using a concave lens.

  • Hypermetropia or long-sightedness is an eye defect where affected person is not able to see close objects clearly. It occurs either due to shifting of the retina in a forward direction or when the focal length of lens increases. It is corrected by using a convex lens.

  • Pressbyopia: It is age-related eye defects where a person is not able to see both far-off and close objects clearly, it occurs due to the weakening of ciliary muscles and hardening of the eye lens. It is corrected by using a bifocal lens which is a combination of both concave and convex lens.

QUESTION: 7

Which of the following actions is/are coordinated by the human brain?

  1. Maintaining blood pressure

  2. Regulating the heartbeat

  3. Balancing the body

Select the correct answer using the code given below.

Solution:
  1. The brain is composed of the cerebrum, cerebellum, and brainstem. The brain receives information through our five senses: sight, smell, touch, taste, and hearing - often many at one time. It assembles the messages in a way that has meaning for us and can store that information in our memory. The brain controls our thoughts, memory and speech, movement of the arms and legs, and the function of many organs within our body.

    1. The cerebrum is the largest part of the brain and is composed of the right and left hemispheres. It performs higher functions like interpreting touch, vision, and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement.

    2. Cerebellum is located under the cerebrum. Its function is to coordinate muscle movements, maintain posture, and balance.

    3. Brainstem: In vertebrate anatomy, the brainstem is the posterior part of the brain adjoining, and structurally continuous with, the spinal cord. Though small, the brainstem is an extremely important part of the brain, as the nerve connections from the motor and sensory systems of the cortex pass through it to communicate with the peripheral nervous system. The brainstem also plays an important role in the regulation of cardiac and respiratory function, consciousness, and the sleep cycle. The brainstem consists of the medulla oblongata, pons, and midbrain.

    4. pons: it contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.

    5. midbrain: it's associated with vision, hearing, motor control, sleep and wake cycles, alertness, and temperature regulation.

    6. medulla oblongata: the lower half of the brainstem that contains the cardiac, respiratory, vomiting, and vasomotor centers and regulates autonomic, involuntary functions such as breathing, heart beat rate, and blood pressure.

  2. Hence all the options are correct.

QUESTION: 8

A man is pushing hard against a rigid brick wall. In this context, which among the following is correct?

Solution:
  • Option (b) is correct.

  • Work (W) is defined as the product of the force (F) and the displacement (s) in the direction of force.

  • W = F x s

  • If force is 1 Newton (N), displacement is 1 metre (m) then work done is 1 Joule (J).

  • Thus, work done by a force acting on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. Work has only magnitude and no direction.

  • If there is no displacement, there is no work done even if the force is large. Thus, when the man pushes hard against a rigid brick wall, the force he exerts on the wall does no work, even though his muscles are alternatively contracting and relaxing and internal energy is being used up.

QUESTION: 9

Which of the following is/are functions of the liver?

  1. Regulation of the glucose levels in the blood

  2. Production of bile

  3. Production of cholesterol in the body

Select the correct answer using the code given below.

Solution:
  • More than 500 vital functions have been identified with the liver. Some of the more well-known functions include the following:

    • Production of bile, which helps carry away waste and break down fats in the small intestine during digestion

    • Production of certain proteins for blood plasma

    • Production of cholesterol and special proteins to help carry fats through the body

    • Conversion of excess glucose into glycogen for storage (glycogen can later be converted back to glucose for energy) and to balance and make glucose as needed

    • Regulation of blood levels of amino acids, which form the building blocks of proteins

    • Processing of hemoglobin for use of its iron content (the liver stores iron)

    • Conversion of poisonous ammonia to urea (urea is an end product of protein metabolism and is excreted in the urine)

    • Clearing the blood of drugs and other poisonous substances

    • Regulating blood clotting

    • Resisting infections by making immune factors and removing bacteria from the bloodstream

    • Clearance of bilirubin, also from red blood cells. If there is an accumulation of bilirubin, the skin and eyes turn yellow.

  • The hormone insulin is a main regulator of the glucose (sugar) levels in the blood. Insulin is produced by the beta cells in the islets of Langerhans in the pancreas.

QUESTION: 10

Duchifat 3, often seen in the news, is

Solution:
  • Three youngsters from an Israeli school were to travel to India to launch a satellite — Duchifat 3 that is designed and built by them aboard PSLV C48 from ISRO’s Sriharikota launch site.

  • This was jointly built by Herzliya Science Center and Sha’ar HaNegev High School students. The satellite is designed to help children “observe the Earth”.

  • The three youngsters Alon Abramovich, Meitav Assulin and Shmuel Aviv Levi who are all 17 to 18 years old, are students of Sha’ar HaNegev High school.

  • Duchifat 3 is the third in the series of the Israeli student-made satellites.

  • It is a photo satellite that is used for ecological research of Earth from space.

  • The size of the satellite is 10x10x30 cm (3U), and it weighs 2.3 kg.

  • Duchifat-3 will be a remote sensing satellite through which the students from all schools in the country will be able to carry out experiments through Earth observation. The satellite will be of good help to agriculturists. This satellite would be a platform for ecological studies such as air pollution, water source pollution, forest monitoring, and more.

  • India was chosen as the spot for the launch because of the success enjoyed by its space program and also the close relations between the two countries.

QUESTION: 11

Which of the pairs given below is/are correctly matched?

Select the correct answer using the code given below.

Solution:
  • Albinism: Albinism is an autosomal recessive mutation. An albino cannot synthesize melanin which provides black coloration to skin and hair. Albinism is due to tyrosinase deficiency. The enzyme tyrosinase normally converts the amino acid tyrosine to melanin through an intermediate product DOPA (dihydro phenylalanine). Hence pair 1 is correctly matched.

  • Cri-du-chat (cat's cry) syndrome: also known as 5p- (5p minus) syndrome, is a chromosomal condition that results when a piece of chromosome 5 is missing. Infants with this condition often have a highpitched cry that sounds like that of a cat. The disorder is characterized by intellectual disability and delayed development, small head size (microcephaly), low birth weight, and weak muscle tone (hypotonia) in infancy. Hence pair 2 is not correctly matched.

  • Cystic fibrosis: The most common lethal genetic disease due to a recessive mutation on chromosome-7. The body produces abnormal glycoprotein which interferes with salt metabolism. The mucus secreted by the body becomes abnormally viscid and blocks passages in the lungs, liver, and pancreas. Hence pair 3 is correctly matched.

QUESTION: 12

Semiconductors are present in most of the modern electronic devices that we use. Which of the following statements is/are true regarding semiconductors?

  1. The resistivity of semiconductors is more than insulators but less than conductors.

  2. The most commonly used semiconductor elements are Silicon and Germanium.

Select the correct answer using the codes given below.

Solution:
  1. Conductors, semiconductors, and insulators are classified on the basis of conductivity/resistivity.

  2. Conductors possess very low resistivity (or high conductivity).

  3. Semiconductors have resistivity or conductivity intermediate to conductors and insulators.

  4. Insulators have high resistivity (or low conductivity).

    1. Thus resistivity of semiconductors is more than conductors but less than insulators. Hence statement 1 is not correct.

  5. Semiconductors can be:

    1. Elemental semiconductors: Silicon(Si) and Germanium(Ge)

    2. Compound semiconductors: Examples are:

      1. Inorganic: CdS, GaAs, CdSe, InP, etc.

      2. Organic: anthracene, doped pthalocyanines, etc.

      3. Organic polymers: polypyrrole, polyaniline, polythiophene, etc.

  6. Most of the currently available semiconductor devices are based on elemental semiconductors Si or Ge and compound inorganic semiconductors. Hence statement 2 is correct.

QUESTION: 13

Consider the following statements:

  1. Saline water has a lower boiling point than distilled water.

  2. Saline water is a good conductor of electricity.

  3. Saline water has a lower freezing point than distilled water.

Which of the statements given above is/are correct?

Solution:
  • Saline water with dissolved salt has free ions. These ions enhance the flow of electrons thus making it a good conductor of electricity.

  • Saline water has a higher boiling point than distilled water. That is it boils at a higher temperature.

  • Saline water has a lower freezing point than distilled water. This property is used to clear ice from the road by sprinkling salt on it.

  • Hence only statement 1 is not correct.

QUESTION: 14

Which of the following methods can be used for removing the permanent hardness of water?

  1. Distillation

  2. Adding sodium carbonate

  3. Boiling

  4. Adding caustic soda

Select the correct answer using the code given below.

Solution:
  • Hard water is water that has high mineral content (in contrast with soft water). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.

  • Hard-drinking water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water.

  • Permanent hardness is caused by dissolved calcium sulphate. Permanent hardness is hardness (mineral content) that cannot be removed by boiling.

  • Distillation can be used to separate and collect a liquid from a solution. Distillation can also be used to soften water as the water evaporates as it is heated and the ions are left behind. Hard water can be softened by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column.

  • Caustic soda (Sodium hydroxide), NaOH removes both temporary and permanent hardness by precipitating the metal ions which cause the hardness as insoluble hydroxides

  • Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate).

  • Hence only options 1, 2 and 4 are correct.

QUESTION: 15

With reference to the Global Consortium for Digital Currency Governance, consider the following statements:

  1. It is the first global consortium focused on designing a framework for the governance of digital currencies.

  2. It is an initiative of the World Economic Forum

Which of the statements given above is/are correct?

Solution:
  • The World Economic Forum recently announced the first global consortium focused on designing a framework for the governance of digital currencies, including stable coins. The Global Consortium for Digital Currency Governance will aim to increase access to the financial system through innovative policy solutions that are inclusive and interoperable.

  • This is the first initiative to bring together leading companies, financial institutions, government representatives, technical experts, academics, international organizations, NGOs and members of the Forum's communities on a global level. • This consortium will focus on solutions for a fragmented regulatory system. Efficiency, speed, inter -operability, inclusivity, and transparency will be at the heart of this initiative. It will call for innovative regulatory approaches to achieve these goals and build trust. A set of guiding principles will be codesigned to support public and private actors exploring the opportunities that digital currencies present.

  • This initiative builds on work done by the World Economic Forum over the past year, convening a global community of central banks to co-design a policy framework for the adoption of digital currencies called the Central Bank Digital Currency Toolkit.

  • Hence both the statements are correct.

QUESTION: 16

Which of the following are vestigial organs of the human body?

Solution:
  • Vestigial organs are organs, tissues or cells in a body which are no more functional the way they were in their ancestral form of the trait. It is authentication of evolution and hence, was helpful in explaining adaptation.

  • Following are a few examples of vestigial organs:

    • Sinuses: Human cheekbones hold the maxillary sinuses. The face consists of pockets of air called sinuses. They are lined by a thin layer of mucosa. It has no significant use but infection can lead to sinusitis.

    • Vermiform Appendix: It is one of the most commonly known vestigial organs. This finger-like tube closed at one end arises from the vermiform process. In prime ancestors, the appendix is believed to have brought about the digestion of cellulose. Today, scientists predict that the appendix may play a role in digestion by bacteria.

    • Coccyx: It forms the last part of the vertebral column, the residue of the lost tail and is often termed as the tailbone. It is observed during human embryogenesis. This formed as the centerpiece of the ‘theory of recapitulation’.

    • Wisdom Tooth: Forms the third set of molars in our buccal cavity. They may have been significant in the past (chewing rough and raw food) but in modern times, as they are inaccessible and remote, it causes pain and infection.

    • External Ear: The Helix (outer rim of the ear) is known to be a vestigial structure. Underdeveloped muscles in the ear make us incapable to bring about the movement of ears. Darwin’s tubercle is a vestigial feature present on the juncture of the upper part of the ear.

    • Nictitating Membrane: Nictitating membrane is the third eyelid found in a few animals that protect and keep the eyes moist and also helps in vision. In humans, it is replaced by plica semilunaris.

    • Tonsils: The tonsils remain as vestigial organs in the human body. They act as the first line of defence and protect the body from harmful microorganisms that are either inhaled or ingested by the body.

QUESTION: 17

Nitrogen gas is used in the tyres of an airplane because

Solution:
  • Aircraft tires are filled with nitrogen because nitrogen gas is mostly inert, meaning that it requires more energy to react with other substances. This is important because, at elevated temperatures, oxygen can react with rubber. Oxidized rubber is weaker than non-oxidized rubber, and weaker tires are not preferred.
  • Air has certain moisture content and it is generally very hard to remove this moisture. If an airplane tires were filled with air, at the flight altitude ice would form inside the tires since the temperature up there is about -30 degrees F. Landing with a chunk of ice in the tire would make it out of balance and change the tire pressure. Tires would probably burst.
  • On the other hand, nitrogen doesn't form a liquid till -173C and pure nitrogen has almost no moisture.
  • Nitrogen being lighter than air does not play a part in it being used in the airplane tyres.
  • Hence option (d) is the correct answer.
QUESTION: 18

The color of the sun appears reddish during sunset. Which of the following is the reason behind this phenomenon?

Solution:

  • As sunlight travels through the earth’s atmosphere, it gets scattered (changes its direction) by the atmospheric particles. Light of shorter wavelengths is scattered much more than light of longer wavelengths. (The amount of scattering is inversely proportional to the fourth power of the wavelength. This is known as Rayleigh scattering). At sunset or sunrise, the sun’s rays have to pass through a larger distance in the atmosphere. Most of the blue and other shorter wavelengths are removed by scattering. The least scattered light reaching our eyes, therefore, the sun looks reddish. This explains the reddish appearance of the sun and full moon near the horizon.
  • This is also the reason that the sky appears blue during the day, as blue has a shorter wavelength than red and is scattered much more strongly. In fact, violet gets scattered even more than blue, having a shorter wavelength. But since our eyes are more sensitive to blue than violet, we see the sky blue.
  • Hence option (c) is the correct answer.
QUESTION: 19

Which of the following can induce mutations?

  1. X rays

  2. Gamma rays

  3. Mustard gas

  4. UV rays

  5. Nitrous acid

Select the correct answer using the code given below.

Solution:
  • A gene mutation is a permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people. Mutations range in size; they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes.

  • Gene mutations can be classified in two major ways:

    • Hereditary mutations are inherited from a parent and are present throughout a person’s life in virtually every cell in the body. These mutations are also called germline mutations because they are present in the parent’s egg or sperm cells, which are also called germ cells. When an egg and a sperm cell unite, the resulting fertilized egg cell receives DNA from both parents. If this DNA has a mutation, the child that grows from the fertilized egg will have the mutation in each of his or her cells.

    • Acquired (or somatic) mutations occur at some time during a person’s life and are present only in certain cells, not in every cell in the body. These changes can be caused by environmental factors such as ultraviolet radiation from the sun or can occur if an error is made as DNA copies itself during cell division. Acquired mutations in somatic cells (cells other than sperm and egg cells) cannot be passed to the next generation

  • Mutation is caused by Xrays; gamma rays; mustard gas, UV rays, nitrous acid etc.

QUESTION: 20

With reference to Bodo tribe in India, consider the following statements:

  1. They are the single largest community among the notified Scheduled Tribes in Assam.

  2. Bodoland Territorial Council is an autonomous body under the Sixth Schedule of the Constitution.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: Bodos are the single largest community among the notified Scheduled Tribes in Assam. Part of the larger umbrella of Bodo-Kachari, the Bodos constitute about 5-6% of Assam’s population. The first organized demand for a Bodo state came in 1967-68 under the banner of the political party Plains Tribals Council of Assam. In 1985, when the Assam Movement culminated in the Assam Accord, many Bodos saw it as essentially focusing on the interests of the Assamese-speaking community.

  • Statement 2 is correct: BTC is an autonomous body under the Sixth Schedule of the Constitution. There have been two Bodo Accords earlier, and the second one led to the formation of BTC. The ABSUled movement from 1987 culminated in a 1993 Bodo Accord, which paved the way for a Bodoland Autonomous Council (BAC), but ABSU withdrew its agreement and renewed its demand for a separate state. In 2003, the second Bodo Accord was signed by the extremist group Bodo Liberation Tiger Force (BLTF), the Centre and the state. This led to the BTC.

  • The area under the jurisdiction of BTC, formed under the 2003 Accord, was called the Bodo Territorial Autonomous District (BTAD). Recently, BTAD was renamed Bodoland Territorial Region (BTR). BTAD comprises Kokrajhar, Chirang, Baksa and Udalguri districts, accounting for 11% of Assam’s area and 10% of its population. BTAD comprises Kokrajhar, Chirang, Baksa and Udalguri districts, accounting for 11% of Assam’s area and 10% of its population.

QUESTION: 21

Consider the following statements with reference to NEST (New and Emerging Strategic technologies):

  1. NEST will negotiate technology governance rules, standards and architecture, suited to India’s conditions, in multilateral and plurilateral frameworks.

  2. It is formed under the Department of Science and Technology.

Which of the statements given above is/are correct?

Solution:
  • The external affairs ministry recently announced the setting up of new, emerging and strategic technologies (NEST) division. Hence statement 2 is not correct.

  • NEST will negotiate technology governance rules, standards, and architecture, suited to India’s conditions, in multilateral and plurilateral frameworks. Hence statement 1 is correct.

  • The development comes close on the heels of the government allowing all network equipment makers, including Huawei, to participate in 5G trials.

  • NEST will act as the nodal division within the ministry for issues pertaining to new and emerging technologies.

  • NEST will negotiate technology governance rules, standards and architecture, suited to India’s conditions, in multilateral and plurilateral frameworks.

  • It will help in collaboration with foreign partners in the field of 5G and artificial intelligence.

  • Its mandate shall include, but not be limited to, evolving India’s external technology policy in coordination with domestic stakeholders and in line with India’s developmental priorities and national security goals.

  • It will also help assess foreign policy and international legal implications of new and emerging technologies and technology-based resources, and recommend appropriate foreign policy choice.

QUESTION: 22

When an ice cube is warmed only to the extent it has totally molten (and not further), how does the temperature change during the entire process from the solid-state to the liquid state?

Solution:
  • If the ambient temperature around a piece of ice increases, the temperature of the ice will increase as well. However, this steady increase in temperature stops as soon as the ice reaches its melting point.

  • At this point, the ice undergoes a change of state and turns into liquid water, and its temperature will not change until all of it has melted.

  • When you heat ice, the individual molecules gain kinetic energy, but until the temperature reaches the melting point, they don't have the energy to break the bonds that hold them in a crystal structure.

  • They vibrate more quickly within their confines as you add heat, and the temperature of the ice goes up. At a critical point – the melting point – they acquire enough energy to break free.

  • When that happens, all the heat energy added to the ice is absorbed by H2O molecules changing phase.

  • There's nothing left to increase the kinetic energy of the molecules in the liquid state until all the bonds holding the molecules in a crystal structure have been broke.

  • Consequently, the temperature remains constant until all the ice has melted.

  • Hence option (a) is the correct answer.

QUESTION: 23

Consider the following statements regarding Nanoflares:

  1. It is a sudden flash of brightness observed by the people living close to the poles at night.

  2. The brightness is generated by converting energy stored in the magnetic field to the motion of plasma.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is not correct: Nanoflares are very small solar flares i.e. sudden flash of brightness observed over the sun’s surface which happens in corona (external atmosphere of the sun). Sun's corona is hotter as compared to the sun's surface. Now scientists have discovered Nano flares to be the reason for this high temperature.

  • Statement 2 is correct: The flash of brightness is related to the conversion of energy stored in the solar magnetic field to the motion of plasma. Plasma motion due to viscosity is converted into heat which results in high energy.

QUESTION: 24

Recently scientists have discovered a new archaeon in Sambhar Salt Lake in Rajasthan. In this context, which of the following correctly describes an Archaeon?

Solution:
  • Archaea (singular archaeon) are a primitive group of microorganisms that thrive in extreme habitats such as hot springs, cold deserts, and hypersaline lakes. These slow-growing organisms are also present in the human gut and have a potential relationship with human health. They are known for producing antimicrobial molecules, and for anti-oxidant activity with applications in eco-friendly wastewater treatment.

  • With a salt production of 0.2 million tonnes per annum, it is also a hypersaline ecosystem that provides an opportunity for microbial ecologists to understand organisms that thrive in such concentrations.

  • The new archaeon has been named Natrialba swarupiae, after Dr. Renu Swarup, Secretary, Department of Biotechnology, for her initiative in supporting microbial diversity studies in the country.

  • An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans.

  • Arachnida is a class of joint-legged invertebrate animals, in the subphylum Chelicerata. Spiders are the largest order in the class, which also includes scorpions, ticks, mites, harvestmen, and solifuges.

  • A mollusc is an animal such as a snail, clam, or octopus which has a soft body. Many types of mollusc have hard shells to protect them.

 

 

 

 

 

QUESTION: 25

ISRO's Project NETRA aims to

(a) explore planets outside the solar system.

(b) aid detection and mapping of ocean bed resources.

(c) provide early warning system in space to detect debris and other hazards to Indian satellites.

(d) ease navigation in metropolitan cities.


Solution:
  • ISRO initiated a project called Project NETRA, which is an early warning system in space to detect debris and other hazards to Indian satellites.

  • Under NETRA the ISRO plans to put up many observational facilities: connected radars, telescopes; data processing units and a control centre. They can, among others, spot, track and catalogue objects as small as 10 cm, up to a range of 3,400 km and equal to a space orbit of around 2,000 km.

  • Project NETRA consists of high-precision, long-range telescope in Leh and a radar in the North East. Along with them, the Multi-Object Tracking Radar (MOTR) at the Satish Dhawan Space Centre in Sriharikota, and the telescopes at Ponmudi and Mount Abu.

  • Hence option (c) is the correct answer.