UPSC Prelims 2019
World Geography Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 2 — Clouds reflect back the Earth's radiation.

Dewdrops form when the Earth's surface cools below the dew point through radiation heat loss on clear nights. On cloudy nights, clouds act as a blanket by reflecting the Earth's longwave radiation back to the surface, preventing sufficient cooling. This keeps the temperature above the dew point, thus preventing dew formation.

📝 Short Notes: Dew Formation and Radiation

• Dew Formation: Dew forms when water vapor in the air condenses on cool surfaces when the surface temperature drops to or below the dew point.
• Radiational Cooling: On clear nights, the Earth's surface radiates heat (longwave infrared radiation) into space, causing surface temperatures to drop rapidly.
• Role of Clouds: Clouds contain water droplets that absorb and reflect back the Earth's outgoing longwave radiation, acting as an insulating blanket.
• Greenhouse Effect: This reflection by clouds is similar to the greenhouse effect, where certain atmospheric components trap heat near the surface.
• Clear vs Cloudy Nights: Clear nights experience maximum cooling and dew formation, while cloudy nights remain warmer with minimal or no dew.
• Dew Point: The temperature at which air becomes saturated (100% relative humidity) and water vapor begins to condense.

Detailed Explanation:

Answer: Option 2 — 1, 3 and 4 only

This question tests knowledge of the geographical boundaries of major seas and their bordering countries. Out of five pairs, three are correctly matched while two contain geographical errors.

✅ Pair 1 – Correct: Albania borders the Adriatic Sea, which separates the Italian Peninsula from the Balkan Peninsula.
❌ Pair 2 – Incorrect: Croatia does not border the Black Sea; it borders the Adriatic Sea. The Black Sea is bordered by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine.
✅ Pair 3 – Correct: Kazakhstan is one of the five littoral states of the Caspian Sea (along with Russia, Turkmenistan, Iran, and Azerbaijan).
✅ Pair 4 – Correct: Morocco borders the Mediterranean Sea along its northern coast.
❌ Pair 5 – Incorrect: Syria does not border the Red Sea; it has a Mediterranean coastline. The Red Sea is bordered by Saudi Arabia, Yemen, Egypt, Sudan, Eritrea, and Djibouti.

📝 Short Notes: Major Seas and Their Littoral States

Detailed Explanation:

Answer: Option 1 — does not set below the horizon at the Arctic Circle

On 21st June, the Northern Hemisphere experiences the Summer Solstice, when the North Pole is tilted at its maximum angle (23.5°) towards the Sun. This results in the Arctic Circle (66.5°N) experiencing 24 hours of continuous daylight, meaning the Sun does not set below the horizon. Conversely, the Antarctic Circle experiences polar night, the Equator has equal day and night, and the Sun is directly overhead at the Tropic of Cancer (not Capricorn).

📝 Short Notes: Solstices and Sun's Position

• Arctic Circle: Located at 66.5°N latitude; experiences midnight sun during summer solstice
• Antarctic Circle: Located at 66.5°S latitude; experiences midnight sun during winter solstice (December)
• Tropic of Cancer: 23.5°N - Sun directly overhead on 21st June
• Tropic of Capricorn: 23.5°S - Sun directly overhead on 22nd December
• Earth's axial tilt: 23.5° from perpendicular to orbital plane causes seasonal variations