1. What are Latitudes?
Latitudes are imaginary horizontal lines drawn parallel to the Equator on the globe.
They measure distance in degrees north or south of the Equator (0°).
Key latitudes:
Key latitudes:
- Equator – 0°
- Tropic of Cancer – 23½° N (passes through India)
- Tropic of Capricorn – 23½° S
- Arctic Circle – 66½° N
- Antarctic Circle – 66½° S
- North Pole – 90° N
- South Pole – 90° S
हिंदी: Latitudes = पूर्व-पश्चिम दिशा में खिंची हुई रेखाएँ, जो Equator के समानांतर होती हैं और
North या South की दूरी बताती हैं। Tropic of Cancer (23½° N) भारत से गुजरती है – ये NDA के लिए बहुत important है।
2. What are Longitudes?
Longitudes are imaginary vertical lines drawn from North Pole to South Pole.
They measure distance in degrees east or west of Prime Meridian (0° longitude),
which passes through Greenwich, London.
Total longitudes: 0° to 180° East and 0° to 180° West.
Total longitudes: 0° to 180° East and 0° to 180° West.
हिंदी: Longitudes = उत्तर से दक्षिण की ओर खिंची रेखाएँ, जो समय (Time) तय करने में सबसे ज़्यादा काम आती हैं।
3. Important Longitude for India
- Standard Meridian of India = 82½° E.
- Indian Standard Time (IST) is based on 82½° E.
- IST is 5 hours 30 minutes ahead of Greenwich Mean Time (GMT).
→ IST = GMT + 5:30
हिंदी: भारत की Standard Time Line – 82½° E (Allahabad के पास)।
IST = GMT + 5:30 – ये fact सीधा exam में पूछा जाता है।
4. Relationship between Longitude & Time
- Earth rotates 360° in 24 hours.
- So, in 1 hour → Earth rotates 15°.
- In 4 minutes → Earth rotates 1° of longitude.
- Moving towards the East → Time increases.
- Moving towards the West → Time decreases.
हिंदी:
- 1° longitude = 4 minutes का समय अंतर।
- पूर्व की ओर जाएँ → समय आगे; पश्चिम की ओर जाएँ → समय पीछे।
5. Simple Example (Time Difference)
If it is 12:00 noon at 0° (GMT), what will be the time at 45° E?
Step:
Difference in longitude = 45°
1° = 4 min ⇒ 45° = 45 × 4 = 180 min = 3 hours
East side → add time
So, Time at 45° E = 12:00 + 3:00 = 3:00 PM.
Step:
Difference in longitude = 45°
1° = 4 min ⇒ 45° = 45 × 4 = 180 min = 3 hours
East side → add time
So, Time at 45° E = 12:00 + 3:00 = 3:00 PM.
हिंदी:
पहले डिग्री का अंतर निकालो → उसे 4 से multiply करो → East हो तो जोड़ो, West हो तो घटाओ।
📘 Practice Questions (NDA Style)
1. Tropic of Cancer is at:
a) 23½° N b) 23½° S c) 66½° N d) 0°
2. Indian Standard Time (IST) is based on which longitude?
a) 0° b) 82½° E c) 23½° N d) 90° E
3. If GMT is 10:00 AM, what will be the IST?
a) 3:30 AM b) 4:30 PM c) 3:30 PM d) 8:30 PM
4. Time difference between two places 30° apart in longitude is:
a) 30 minutes b) 1 hour c) 2 hours d) 3 hours
a) 23½° N b) 23½° S c) 66½° N d) 0°
2. Indian Standard Time (IST) is based on which longitude?
a) 0° b) 82½° E c) 23½° N d) 90° E
3. If GMT is 10:00 AM, what will be the IST?
a) 3:30 AM b) 4:30 PM c) 3:30 PM d) 8:30 PM
4. Time difference between two places 30° apart in longitude is:
a) 30 minutes b) 1 hour c) 2 hours d) 3 hours
Answers:
1 – a) 23½° N
2 – b) 82½° E
3 – c) 3:30 PM (10:00 + 5:30)
4 – b) 1 hour (30° × 4 min = 120 min = 2 hours) ❗
Note: Carefully revise: 15° = 1 hour → 30° = 2 hours. So the correct answer is actually: 2 hours. If option given is (c) 2 hours, mark that.
1 – a) 23½° N
2 – b) 82½° E
3 – c) 3:30 PM (10:00 + 5:30)
4 – b) 1 hour (30° × 4 min = 120 min = 2 hours) ❗
Note: Carefully revise: 15° = 1 hour → 30° = 2 hours. So the correct answer is actually: 2 hours. If option given is (c) 2 hours, mark that.
Quick Recap | सार
Now you should be able to:
- Recall the most important ideas of this topic.
- Solve typical NDA-style questions from this chapter.
- Spot and avoid common traps used in competitive exams.
Self-check: 3–4 random questions उठा कर देखिए – अगर आसानी से हो रहे हैं, तो chapter strong है।
Common Exam Mistakes | आम गलतियाँ
- Concept ठीक से clear न करना और सीधे रटने की कोशिश करना।
- Question पूरी तरह पढ़े बिना answer mark कर देना।
- Figures, dates, या formulas को last step में verify न करना।
NDA में smart strategy यह है कि आसान वाले सवाल पहले, doubtful बाद में – और silly mistakes से बचना सबसे ज़रूरी है।