UPSC 2024. On June 21 every year, which of the following latitude(s) experience(s) a sunlight of more than 12 hours?

1. Equator — NO — exactly 12 hours
2. Tropic of Cancer — YES — about 13.5 hours
3. Tropic of Capricorn — NO — about 10.5 hours
4. Arctic Circle — YES — 24 hours

Answer: (d) 2 and 4

Remember: 21 June: north of the equator > 12 h · equator = 12 h · south < 12 h · Arctic Circle and above = 24 h.

UPSC 2019. On 21st June, the Sun

Answer: (a) does not set below the horizon at the Arctic Circle

Remember: 21 June: Sun overhead at the Tropic of Cancer · 24 h day at the Arctic Circle · 24 h night at the Antarctic Circle.

UPSC 2024. Statement-I: Giant stars live much longer than dwarf stars. Statement-II: Compared to dwarf stars, giant stars have a greater rate of nuclear reactions. Which one of the following is correct in respect of the above statements?

Answer: (d) Statement-I is incorrect, but Statement-II is correct

Remember: Big star = fast fusion = short life. Small star (red dwarf, Sun) = slow fusion = long life.

UPSC 2018. Among the following cities, which one lies on a longitude closest to that of Delhi?

Answer: (a) Bengaluru

Remember: Delhi and Bengaluru ≈ 77°E. India’s standard meridian is 82.5°E (Mirzapur).

UPSC 2014. What is the correct sequence of occurrence of the following cities in South-East Asia as one proceeds from south to north? 1. Bangkok 2. Hanoi 3. Jakarta 4. Singapore

Answer: (c) 3 – 4 – 1 – 2

Remember: South → north: Jakarta (6°S) · Singapore (1°N) · Bangkok (14°N) · Hanoi (21°N).

UPSC 2026. Tungurahua Volcano, which was declared a Global Geopark by UNESCO in 2025, is situated in which one among the following countries?

Answer: (a) Ecuador

Remember: Tungurahua = Ecuador · UNESCO Global Geopark (2025) · Ring of Fire volcano.

UPSC 2025. Which of the following are the evidences of the phenomenon of continental drift?

1. The belt of ancient rocks from Brazil coast matches with those from Western Africa. — CORRECT
2. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side. — CORRECT
3. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere. — CORRECT

Answer: (c) I, II and III

Remember: Drift evidence: coast fit · same-age rocks (Brazil–W Africa) · tillite · Ghana gold from Brazil · Gondwana sediments on six landmasses.

UPSC 2025. Statement I: In the context of effect of water on rocks, chalk is known as a very permeable rock whereas clay is known as quite an impermeable or least permeable rock. Statement II: Chalk is porous and hence can absorb water. Statement III: Clay is not at all porous. Which one of the following is correct?

Answer: (c) Only one of II and III is correct and that explains I

Remember: Chalk: porous + permeable. Clay: very porous but impermeable — that’s why it seals aquifers and ponds.

UPSC 2023. Consider the following statements:

1. In a seismograph, P waves are recorded earlier than S waves. — CORRECT
2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation. — CORRECT

Answer: (c) Both 1 and 2

Remember: P = primary, fastest, longitudinal, all media. S = secondary, transverse, solids only.

UPSC 2024. Consider the following: 1. Pyroclastic debris 2. Ash and dust 3. Nitrogen compounds 4. Sulphur compounds. How many of the above are products of volcanic eruptions?

Answer: (d) All four

Remember: Volcanic products: lava, pyroclastic debris, ash/dust, gases (water vapour, CO₂, sulphur and nitrogen compounds).

UPSC 2025. Statement I: In January, in the Northern Hemisphere, the isotherms bend equatorward while crossing the landmasses, and poleward while crossing the oceans. Statement II: In January, the air over the oceans is warmer than that over the landmasses in the Northern Hemisphere. Which one of the following is correct?

Answer: (a) Both are correct and Statement II explains Statement I

Remember: January (N. hemisphere): isotherms bend poleward over oceans, equatorward over land — the ocean is warmer. July: the reverse.

UPSC 2025. Statement I: The amount of dust particles in the atmosphere is more in subtropical and temperate areas than in equatorial and polar regions. Statement II: Subtropical and temperate areas have less dry winds. Which one of the following is correct?

Answer: (c) Statement I is correct but Statement II is not correct

Remember: Most dust: subtropical and temperate belts (dry winds, deserts). Least: equator (rain washes it out) and poles (ice).

UPSC 2024. Statement-I: Thickness of the troposphere at the equator is much greater as compared to poles. Statement-II: At the equator, heat is transported to great heights by strong convectional currents. Which one of the following is correct?

Answer: (a) Both are correct and Statement-II explains Statement-I

Remember: Troposphere: ~18 km at the equator, ~8 km at the poles — convection sets its height.

UPSC 2022. Consider the following statements:

1. High clouds primarily reflect solar radiation and cool the surface of the Earth. — WRONG — high clouds warm
2. Low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause a warming effect. — WRONG — low clouds cool

Answer: (d) Neither 1 nor 2

Remember: High clouds (cirrus) → net warming. Low clouds (stratus) → net cooling.

UPSC 2019. Why are dewdrops not formed on a cloudy night?

Answer: (b) Clouds reflect the Earth’s radiation.

Remember: Dew needs a clear, calm night. Clouds = a blanket that keeps the ground warm.

UPSC 2026. Ships from which of the following countries have to cross the Strait of Hormuz to reach out to the Indian Ocean?

1. Bahrain — YES — an island inside the Persian Gulf
2. Syria — NO — Mediterranean coast
3. Qatar — YES — a peninsula in the Gulf
4. Egypt — NO — Red Sea coast

Answer: (b) 1 and 3

Remember: Hormuz-locked: Kuwait, Iraq, Bahrain, Qatar. Red Sea exit: Bab-el-Mandeb. Mediterranean exit: Suez.

UPSC 2024. Consider the following countries: 1. Finland 2. Germany 3. Norway 4. Russia. How many of the above countries have a border with the North Sea?

Answer: (b) Only two

Remember: North Sea: UK, Norway, Denmark, Germany, Netherlands, Belgium, France. Baltic: Finland, Russia, Sweden, the Baltic States, Poland.

UPSC 2024. With reference to “Coriolis force”, which of the following statements is/are correct?

1. It increases with increase in wind velocity. — CORRECT
2. It is maximum at the poles and is absent at the equator. — CORRECT

Answer: (c) Both 1 and 2

Remember: Coriolis ∝ wind speed × sin(latitude): zero at the equator, maximum at the poles; right in the north, left in the south.

UPSC 2021. Consider the following statements:

1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds. — CORRECT
2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections. — CORRECT

Answer: (c) Both 1 and 2

Remember: Tropics (trades): west side warm. Temperate (westerlies): east side warm.

UPSC 2015. What explains the eastward flow of the equatorial counter-current?

Answer: (b) Convergence of the two equatorial currents

Remember: Equatorial counter-current = return flow of water piled up in the west by the two westward equatorial currents.

UPSC 2025. Consider the following countries: I. Bolivia II. Brazil III. Colombia IV. Ecuador V. Paraguay VI. Venezuela. Andes mountains pass through how many of the above countries?

1. Bolivia — YES
2. Brazil — NO
3. Colombia — YES
4. Ecuador — YES
5. Paraguay — NO
6. Venezuela — YES

Answer: (c) Only four

Remember: Andes countries (7): Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, Argentina. Not Brazil, Paraguay, Uruguay.

UPSC 2025. Consider the following water bodies: I. Lake Tanganyika II. Lake Tonle Sap III. Patos Lagoon. Through how many of them does the equator pass?

1. Lake Tanganyika — NO — about 3°–9°S
2. Lake Tonle Sap — NO — about 13°N
3. Patos Lagoon — NO — about 31°S

Answer: (d) None

Remember: Equator crosses: Lake Victoria · Amazon mouth · Sumatra, Borneo, Sulawesi · south of the Maldives. Not Tanganyika.

UPSC 2024. One of the following regions has the world’s largest tropical peatland, which holds about three years’ worth of global carbon emissions from fossil fuels; and the possible destruction of which can exert detrimental effect on the global climate. Which one of the following denotes that region?

Answer: (b) Congo Basin

Remember: Largest tropical peatland = Cuvette Centrale, Congo Basin (~30 billion tonnes of carbon).

UPSC 2023. About three-fourths of world’s cobalt, a metal required for the manufacture of batteries for electric motor vehicles, is produced by

Answer: (c) The Democratic Republic of the Congo

Remember: Cobalt = DR Congo (~75%). Lithium = Australia + the South American triangle. Uranium = Kazakhstan. Diamonds = Botswana (value), Russia (volume).

UPSC 2018. Which of the following has/have shrunk immensely/dried up in the recent past due to human activities? 1. Aral Sea 2. Black Sea 3. Lake Baikal

Answer: (a) 1 only

Remember: Aral Sea (Kazakhstan–Uzbekistan) = the textbook human-made shrinking. Lake Chad in Africa has also shrunk sharply.