UPSC Prelims 2024 Q15: Geography – Astronomy & Earth - Sun System
On June 21 every year, which of the following latitude(s) experience(s) a sunlight of more
than 12 hours ?
1. Equator
2. Tropic of Cancer
3. Tropic of Capricorn
4. Arctic Circle
Select the correct answer using the code given below :
- (a) 1 only
- (b) 2 only
- (c) 3 and 4
- (d) 2 and 4
Answer: (d) 2 and 4
Explanation
Daylight on June 21 (summer solstice)
On June 21 the Sun is overhead at the Tropic of Cancer.
The Northern Hemisphere is tilted towards the Sun, so days there are longer than nights.
| Latitude | Daylight on June 21 | More than 12 hours? |
|---|---|---|
| 1. Equator | 12 hours, as on every day of the year | No |
| 2. Tropic of Cancer | About 13.5 hours | Yes |
| 3. Tropic of Capricorn | About 10.5 hours; it is winter there | No |
| 4. Arctic Circle | 24 hours (the midnight sun) | Yes |
The rule for June 21:
| Place | Length of day |
|---|---|
| North of the Equator | More than 12 hours; grows longer towards the pole |
| Equator | Equal day and night |
| South of the Equator | Less than 12 hours |
| Antarctic Circle | No sunlight (polar night) |
Only the Tropic of Cancer and the Arctic Circle get more than 12 hours.
Answer: (d) 2 and 4.
Why each option is right or wrong
- (a) Incorrect. The Equator has 12 hours of sunlight, not more than 12.
- (b) Incorrect. The Arctic Circle also gets more than 12 hours; it has 24 hours of sunlight.
- (c) Incorrect. The Tropic of Capricorn is in winter on June 21 and gets less than 12 hours.
- (d) CORRECT. The Tropic of Cancer and the Arctic Circle are both north of the Equator.
Key point
June 21: Sun overhead at the Tropic of Cancer; days longer than 12 hours everywhere north of the Equator; 24 hours at the Arctic Circle; Equator always 12 hours.
Remember
June 21: north gets long days, south gets short days, Equator stays at 12.
Common mistakes
- Including the Equator; its day is always 12 hours, never more.
- Forgetting that the Tropic of Capricorn is in the Southern Hemisphere.
- Thinking only the Tropic of Cancer counts because the Sun is overhead there.
Exam tip
On June 21, every latitude north of the Equator has a day longer than 12 hours. Just sort the list into north and south.
Sources
- NCERT Class VI — The Earth: Our Habitat, Ch 3 (Motions of the Earth)
- NCERT Class XI — Fundamentals of Physical Geography, Ch 9 (Solar Radiation, Heat Balance and Temperature)