UPSC Previous Year GK Questions with Answers

The correct answer is B, 1, 2 and 3. All three subjects sit in the list named against them in the Seventh Schedule.

The Seventh Schedule, read with Article 246, divides law-making powers into three lists. Public health and sanitation, hospitals and dispensaries is entry 6 of the State List, so states run most health services. Citizenship, naturalisation and aliens is entry 17 of the Union List, which is why only Parliament made the Citizenship Act, 1955. Legal, medical and other professions is entry 26 of the Concurrent List, so both Parliament and the states can make laws on them, as with the Advocates Act and the National Medical Commission Act.

A is wrong: pair 1 is correct, but pairs 2 and 3 are correct too.

C is wrong: it leaves out the correct pair 1.

D is wrong: it leaves out the correct pairs 1 and 2.

Exam tip: Seventh Schedule with Article 246; public health = State List, citizenship = Union List, professions = Concurrent List.

The correct answer is A, fireworks to make a bright white light. Magnesium burns in air with a dazzling white flame, which is why it goes into fireworks, sparklers and flares.

When magnesium ribbon is heated it reacts with oxygen to form white magnesium oxide (2Mg + O2 → 2MgO), giving out intense heat and brilliant white light, including ultraviolet. Pyrotechnic makers add magnesium or magnesium-aluminium alloy powder to brighten colours and produce white sparks; the same property was used in early photographic flash powder. Magnesium is also the central atom of chlorophyll and a light metal used in alloys for aircraft and car parts.

B is wrong: gemstones are minerals such as corundum, beryl or diamond, not magnesium metal.

C is wrong: the alimentary canal is examined with a barium meal, using barium sulphate, which shows up in X-rays.

D is wrong: water is purified with chlorine, bleaching powder, alum or ozone, not magnesium.

Exam tip: magnesium = white flame and the centre of chlorophyll; barium = green flame and the barium meal; strontium = red flame.

The correct answer is B. A short-sighted (myopic) person sees near things clearly but distant things blurred, and a concave lens corrects it.

In myopia the eyeball is too long or the eye lens too strongly curved, so light from a distant object comes to a focus in front of the retina instead of on it. The far point of the eye moves closer than infinity. A concave (diverging) lens of suitable power spreads the incoming rays slightly, so they focus exactly on the retina. Its power is negative, measured in dioptres.

A is wrong: blurred near vision with clear distant vision is long-sightedness (hypermetropia), and both the defect and the lens are mismatched here.

C is wrong: it describes hypermetropia but pairs it with a concave lens.

D is wrong: the symptoms are right for myopia, but a convex lens would make it worse.

Exam tip: myopia = near clear, far blurred, concave lens; hypermetropia = far clear, near blurred, convex lens; presbyopia = age, often bifocals.

The correct answer is A, 1 and 3. A compound microscope uses two convex lenses, and its magnification depends on the tube length.

The objective is a convex lens of very short focal length that forms a real, enlarged image of the specimen. The eyepiece is also a convex lens and works like a magnifying glass on that image. The total magnification is roughly (L/fo) × (D/fe), where L is the tube length, D is 25 cm, the least distance of distinct vision, and fo and fe are the focal lengths of the objective and eyepiece. So a longer tube gives more magnification, while a longer focal length gives less.

B is wrong: statement 3 is true, but statement 1 is also true, so 3 alone is incomplete.

C is wrong: statement 4 is false, because the eyepiece is convex, not concave.

D is wrong: statement 2 is false, since magnification falls as the objective's focal length rises, and statement 4 is false as well.

Exam tip: microscope = two convex lenses, objective of short focal length; telescope objective has a long focal length.

The correct answer is C. The third law does not make one force the cause and the other the effect; action and reaction arise together, at the same instant.

Newton's third law says that to every action there is an equal and opposite reaction. The two forces act on two different bodies, are equal in size, opposite in direction and simultaneous. Because neither comes first, the words action and reaction are only labels; either force can be called the action. This is also why forces always come in pairs in nature.

A is correct and so not the answer: a force is always an interaction between two bodies, so it never occurs alone.

B is correct and so not the answer: the stone pulls the Earth upwards with the same force; the Earth barely moves because its mass is enormous.

D is correct and so not the answer: it is the accurate reading of the law, that action and reaction are simultaneous, with no cause and effect between them.

Exam tip: action and reaction are equal, opposite, simultaneous and act on different bodies, so they never cancel each other.

The correct answer is A, 5 cm, converging. A real, inverted image of the same size forms only when the object sits at twice the focal length of a convex lens, so 2f = 10 cm and f = 5 cm.

For a convex (converging) lens, an object placed at 2F gives a real, inverted image of equal size at 2F on the other side. Check with the lens formula 1/v − 1/u = 1/f: with u = −10 cm and v = +10 cm, 1/f = 1/10 + 1/10 = 1/5, so f = +5 cm. A positive focal length confirms a converging lens. Magnification m = v/u = −1, which means same size and inverted.

B is wrong: a diverging (concave) lens always forms a virtual, erect and diminished image, never a real one.

C is wrong: with f = 20 cm the object at 10 cm would be inside the focus and the image would be virtual and enlarged.

D is wrong: a concave lens cannot form a real image, whatever its focal length.

Exam tip: convex lens, object at 2F gives image at 2F, real, inverted and the same size; u = v = 2f.

The correct answer is C: the chamber lets short-wavelength radiation in but does not let long-wavelength infrared out, so heat is trapped.

Sunlight reaching a glasshouse is mostly visible light and short-wavelength (near) infrared, which glass transmits easily. The plants and soil inside absorb it, warm up and re-radiate the energy as long-wavelength infrared, because cooler bodies emit at longer wavelengths. Glass is largely opaque to this long-wave radiation, so the energy stays inside and the temperature rises. In the atmosphere, carbon dioxide, water vapour, methane and nitrous oxide play the role of the glass, keeping the Earth about 33 °C warmer than it would otherwise be.

A is wrong: if no radiation entered, there would be no energy to trap.

B is wrong: it reverses the wavelengths; long waves are the ones held back.

D is wrong: if all infrared could escape freely, nothing would be trapped and no warming would occur.

Exam tip: in short, out long; glass and greenhouse gases stop the outgoing long-wave infrared.

The correct answer is C, Statement I is true but Statement II is false. Plantations do lie mostly in the humid tropics, but the soils there are generally poor, not highly fertile.

Plantation farming grows a single cash crop such as tea, coffee, rubber, sugarcane, cocoa, banana or oil palm on large estates with heavy capital and hired labour. It spread in the humid tropics of Asia, Africa and Latin America, largely under colonial rule, because these crops need high temperatures and heavy rain throughout the year. The same heavy rain leaches nutrients out of the soil, leaving laterite and other weathered red soils that are low in humus and plant food; the lush forest survives by quickly recycling nutrients from fallen leaves.

A is wrong: Statement II is false, so it cannot explain Statement I.

B is wrong: it treats the false Statement II as true.

D is wrong: Statement I is true and Statement II is false, the reverse of this option.

Exam tip: humid tropics have lush forest but leached, infertile laterite soil; plantations need the climate, not rich soil.

The correct answer is C, total internal reflection. Light inside the fibre strikes the boundary at more than the critical angle, so it is reflected back again and again instead of escaping.

An optical fibre has a glass core surrounded by cladding of slightly lower refractive index. Total internal reflection happens when light travels from a denser to a rarer medium and the angle of incidence is greater than the critical angle. Each time the signal meets the core-cladding boundary it is fully reflected, so it zigzags along the fibre with very little loss, even around gentle bends. This is why fibres carry internet and telephone data over long distances and are used in endoscopes.

A is wrong: interference is the overlapping of waves to form bright and dark bands.

B is wrong: scattering spreads light out, as in the blue sky, and is a source of loss in a fibre.

D is wrong: refraction lets light pass out of the core; the fibre works because light does not refract out.

Exam tip: two conditions for total internal reflection are denser to rarer medium and angle above the critical angle; examples are optical fibre, sparkling diamond and mirage.

The correct answer is B, 1 and 2 only. A short notice question is an urgent oral question taken up only with the Minister's consent, and it is answered after Question Hour, not during it.

Under the Rules of Procedure of the Lok Sabha, a member may ask a question on a matter of urgent public importance with less than the usual ten clear days' notice, stating the reason for urgency. It is admitted only if the Minister concerned agrees to answer it at short notice. Such a question is taken up for oral answer immediately after the questions for oral answer of that day have been disposed of, that is, after Question Hour.

A is wrong: it includes statement 3, but these questions come after Question Hour.

C is wrong: it drops the true statement 1 and keeps the false statement 3.

D is wrong: it keeps statement 3 and leaves out the true statement 2.

Exam tip: starred = oral, unstarred = written, short notice = urgent, under ten days, needs the Minister's consent, taken after Question Hour.

The correct answer is C, Doppler effect. A speed radar measures how much the frequency of its reflected wave changes, and that change depends on the speed of the vehicle.

The Doppler effect, described by Christian Doppler in 1842, is the apparent change in the frequency of a wave when the source and the observer move relative to each other. The police gun sends out radio waves of a fixed frequency; a car coming towards it reflects them at a higher frequency, a car moving away at a lower one. The device converts this frequency shift into the speed of the vehicle. The same idea explains the falling pitch of a passing train's horn and the red shift of distant galaxies.

A is wrong: the Raman effect is the scattering of light by molecules with a change of wavelength, found by C. V. Raman in 1928.

B is wrong: induction is about producing current by a changing magnetic field.

D is wrong: Coulomb's law gives the force between electric charges.

Exam tip: speed gun, passing horn and red shift of galaxies all use the Doppler effect.

The correct answer is C, Infrared and microwave radiations. Both kinds of radiation carry energy that food absorbs as heat, and both are used in everyday kitchens.

Infrared radiation is the heat radiation given out by hot bodies: a grill, a toaster, an oven element or glowing coals cook the surface of food mainly by infrared rays. A microwave oven uses microwaves of about 2.45 GHz; water molecules in the food are polar, so they keep turning with the oscillating field and the friction heats the food from within. So two different bands of the spectrum are put to use in cooking.

A is wrong: infrared is used, but it leaves out the microwave oven.

B is wrong: microwaves are used, but grills and toasters cook with infrared.

D is wrong: X-rays, gamma rays and ultraviolet are harmful ionising or high-energy radiations and radio waves carry too little energy; none of them is used to cook.

Exam tip: microwave oven = about 2.45 GHz, heats water molecules; grill and toaster = infrared.

The correct answer is A, 1 only. In January the northern oceans are warmer than the frozen continents, so isotherms bend north over the sea and south over the land; the Gulf Stream and North Atlantic Drift are warm currents, not cold ones.

Isotherms are lines joining places of equal temperature. In the northern hemisphere winter, land loses heat quickly and becomes very cold, while the ocean keeps its warmth. A given temperature is therefore found further north over the ocean and further south over the continents such as Siberia, which makes the lines bend. Statement 2 is wrong: the Gulf Stream and the North Atlantic Drift carry warm tropical water into the North Atlantic, making it warmer, and that warmth is why the isotherms bend sharply north there, keeping ports of north-west Europe ice-free.

B is wrong because statement 2 calls warm currents cold.

C is wrong because statement 2 is false.

D is wrong because statement 1 is a correct inference.

Exam tip: January isotherms bend poleward over oceans and equatorward over land; Gulf Stream and North Atlantic Drift are warm currents.

The correct answer is A, Privileges. Equality means that no person or group enjoys special rights denied to others, so it implies the absence of privileges.

In political theory, equality rests on the idea that all people deserve equal concern and respect. Harold Laski described equality first of all as the absence of special privilege, along with adequate opportunities for all. The Indian Constitution reflects this: Article 14 gives equality before the law, Article 15 bars discrimination, Article 17 abolishes untouchability and Article 18 abolishes titles, all of which remove privileges based on birth, caste or status.

B is wrong because a society of equals still has laws and restraints that apply to everyone alike.

C is wrong because equality of opportunity actually allows fair competition rather than removing it.

D is wrong because equality is itself an ideal and does not require the absence of ideology.

Exam tip: Laski: equality means the absence of special privilege and adequate opportunities for all; Articles 14 to 18 are the Right to Equality.

The correct answer is C, World Economic Forum. The Global Competitiveness Report is the World Economic Forum's assessment of how well countries' institutions, policies and markets support productivity and growth.

The World Economic Forum is a Geneva-based not-for-profit foundation, set up by Klaus Schwab in 1971 and known for its annual meeting at Davos, Switzerland. Its Global Competitiveness Report, first brought out in 1979, ranks economies on a Global Competitiveness Index built on pillars such as institutions, infrastructure, macroeconomic stability, health, skills, markets and innovation. The WEF also publishes the Global Gender Gap Report and the Global Risks Report.

A is wrong: the IMF publishes the World Economic Outlook and the Global Financial Stability Report.

B is wrong: UNCTAD publishes the World Investment Report and the Trade and Development Report.

D is wrong: the World Bank published the Doing Business Report and publishes the World Development Report.

Exam tip: WEF = Global Competitiveness, Global Gender Gap and Global Risks reports; IMF = World Economic Outlook.

The correct answer is D, 1, 2 and 3. Indian bond yields respond to the RBI's policy, to domestic inflation and short-term rates, and also to the US Federal Reserve through global capital flows.

A bond's yield is the return an investor earns on it, and it moves opposite to the bond's price. When the RBI cuts the repo rate or buys government securities through open market operations, yields tend to fall; tightening pushes them up. Higher inflation makes investors demand a higher return, and short-term rates set the base from which longer yields are priced. When the US Federal Reserve raises rates, foreign investors may pull money out of Indian bonds for safer US assets, which lowers bond prices in India and lifts yields.

A is wrong because inflation and short-term rates also matter.

B is wrong because the RBI is only one of several influences.

C is wrong because both central banks also move yields.

Exam tip: bond price and yield move in opposite directions; inflation up, yields up.

The correct answer is C, Both 1 and 2. The Common Framework for Debt Treatments was agreed by the G20 and the Paris Club in November 2020 to help low-income countries with unsustainable debt.

During the COVID-19 crisis many poor countries could not service their loans. The G20 first offered the Debt Service Suspension Initiative (DSSI), which only postponed payments. The Common Framework went further: it lets eligible countries (those eligible for the DSSI) seek a full restructuring of their official bilateral debt, with all G20 creditors, including newer lenders outside the Paris Club such as China and India, negotiating together on comparable terms. The Paris Club is an informal group of major creditor countries that coordinates solutions for debtor nations.

A is wrong because statement 2, its purpose, is also correct.

B is wrong because the framework was indeed endorsed by the G20 together with the Paris Club.

D is wrong because both statements describe the framework correctly.

Exam tip: DSSI postponed debt payments; the Common Framework (2020) restructures debt of low-income countries.

The correct answer is B, Only two. Mahua and teak shed their leaves in the dry season, while the jackfruit tree is evergreen.

Deciduous trees drop all their leaves for a few weeks in the dry summer to save water; they make up India's tropical moist and dry deciduous forests, the most widespread forest type in the country. Teak is the best-known tree of these forests, found in Madhya Pradesh, Maharashtra, Karnataka and Kerala. Mahua is a deciduous tree of central India whose flowers are eaten and used to make liquor, and whose seeds give oil; it matters greatly to tribal communities. The jackfruit, by contrast, keeps its glossy leaves all year and grows in the humid Western Ghats and coastal regions.

A is wrong because two of the trees, not one, are deciduous.

C is wrong because the jackfruit is evergreen.

D is wrong because teak and mahua are typical deciduous trees.

Exam tip: teak, sal, mahua, sandalwood = deciduous; jackfruit, rosewood, mahogany = evergreen.

The correct answer is D, All four. A volcanic eruption throws out solid fragments, fine ash and dust, and a mixture of gases that includes nitrogen and sulphur compounds.

Material released by a volcano is of three kinds. Solid matter includes pyroclastic debris, the broken pieces of rock and lava blown out by the explosion, ranging from large volcanic bombs to small lapilli, along with fine ash and dust that can spread across continents. Liquid matter is the lava. Gases are mostly water vapour, followed by carbon dioxide, sulphur compounds such as sulphur dioxide and hydrogen sulphide, and nitrogen compounds, with smaller amounts of chlorine, hydrogen and argon. Sulphur dioxide forms sulphate aerosols in the stratosphere that can cool the climate for a year or two.

A is wrong because more than one item is a volcanic product.

B is wrong because the gases, not only the solids, come from eruptions.

C is wrong because none of the four can be left out.

Exam tip: volcanic gases = mostly water vapour, then carbon dioxide, sulphur and nitrogen compounds.

The correct answer is B, plan of action outlined by the countries of the world to combat climate change. INDCs were the climate pledges countries announced before the Paris climate conference of 2015.

Under the UN Framework Convention on Climate Change, each country was asked to state what it intended to do to cut greenhouse gas emissions and adapt to climate change after 2020. These Intended Nationally Determined Contributions were submitted before COP21 in Paris in December 2015. Once a country ratified the Paris Agreement, its INDC became its Nationally Determined Contribution (NDC), to be updated every five years with greater ambition. India's first INDC was submitted in October 2015.

A is wrong because refugee pledges have nothing to do with this term.

C is wrong because capital subscriptions to the AIIB are not called INDCs.

D is wrong because the Sustainable Development Goals are pursued through the 2030 Agenda, not through INDCs.

Exam tip: INDC before Paris (COP21, 2015) became NDC after ratification, revised every five years.