Geography Important Questions Chapter 7 International Date Line Class 9 Maharashtra Board

Imp Questions For All Chapters – Geography Class 9th

Short Questions

1. Which meridian serves as the reference for Greenwich Mean Time (GMT)?

• The 0° meridian, also called the Prime Meridian.

2. What specific meridian defines Indian Standard Time (IST)?

• The 82.5° E meridian.

3. How many minutes ahead is IST compared to GMT?

• 330 minutes (5 hours and 30 minutes).

4. According to IST, which location welcomed 2017 earliest on Saturday?

• Samoa Island (Apia) at 15:30.

5. Which location was the last to farewell 2016 as per the IST table?

• Baker Island at 17:30 on Sunday.

6. On what day did New York enter 2017 according to IST?

• Sunday at 10:30.

7. What imaginary line near 180° meridian marks a change in calendar dates?

• The International Date Line (IDL).

8. What global problem does the IDL solve for travelers?

• It prevents confusion in dates across time zones.

9. Why was the Pacific Ocean chosen for most of the IDL’s path?

• To avoid splitting landmasses with different dates.

10. What adjustment is made to the date when crossing the IDL from Japan to the USA?

• Subtract one day (e.g., Tuesday becomes Monday).

11. How does crossing the IDL from east to west affect the calendar?

• You add one day (e.g., Monday becomes Tuesday).

12. How many degrees does Earth rotate in one hour?

• 15° (360° ÷ 24 hours).

13. What causes the eastern part of Earth to be ahead in time?

• Earth’s west-to-east rotation makes the east see the sun first.

14. In what year was the IDL officially established by international agreement?

• 1884, led by Professor Davidson.

15. Why does the IDL deviate from the straight 180° meridian?

• It bends to keep islands and countries on the same date.

16. What is the time at 120° E when it’s 12 noon at Greenwich?

• 20:00 (8 p.m.) on the same day (120° ÷ 15 = 8 hours ahead).

17. If it’s 12 noon at 0°, what time is it at 150° W?

• 02:00 (2 a.m.) on the same day (150° ÷ 15 = 10 hours behind).

18. How does the IDL assist international airline schedules?

• It ensures accurate date and time changes for flights crossing it.

19. Which side of the IDL experiences the end of a day first?

• The eastern side (e.g., USA) ends the day as the west begins it.

20. What significant adjustment to the IDL was made in 2011?

• It was shifted to keep certain Pacific islands on the same date.

Long Questions

1. How does the IST table show the sequence of New Year 2017 across locations?

• Samoa Island welcomed 2017 first at 15:30 Saturday IST, being west of the IDL, while Baker Island was last at 17:30 Sunday IST, east of the IDL. This shows how the IDL and Earth’s rotation set the order of the new day globally.

2. Why did Sunil think it was Friday and Meenal think it was Wednesday after their journey?

• Sunil traveled east, crossing the IDL from west to east, losing a day (Thursday to Friday), while Meenal went west, gaining a day (Thursday to Wednesday). Their opposite directions around the 180° meridian caused the day difference.

3. What happens to the date when flying from Tokyo to San Francisco across the IDL?

• Flying from Tokyo (west of IDL) to San Francisco (east of IDL), you subtract a day, like from Tuesday 2nd to Monday 1st. This keeps the date consistent with the eastward travel rule of the IDL.

4. Why was the IDL created near the 180° meridian instead of another line?

• The 180° meridian is opposite the 0° Greenwich meridian, making it a logical spot for a date change as Earth rotates. In 1884, it was chosen to standardize time and avoid confusion across the globe.

5. How does the IDL’s path through the Pacific Ocean prevent practical issues?

• By running through the ocean, the IDL avoids splitting land areas like islands, which would have different dates on each side. This keeps entire communities on the same day, making life and travel simpler.

6. How does Earth’s rotation influence time changes as shown in Sunil’s journey?

• Earth rotates west to east, so as Sunil moved east, time advanced (e.g., 12 noon Thursday at 0° to 12 midnight at 180°). Crossing the IDL eastward, he lost a day, reaching Friday at 0° due to the date adjustment.

7. Why is adjusting the date necessary when crossing the IDL from America to Japan?

• From America (east of IDL) to Japan (west of IDL), you add a day (e.g., Friday 5th to Saturday 6th) to match the new day starting west of the line. This adjustment keeps global time coordinated as Earth rotates.

8. What role did the 1884 conference play in establishing the IDL?

• In 1884, nations met under Professor Davidson to set the IDL near the 180° meridian for a unified global time system. This solved the problem of where a day starts and ends on a round Earth.

9. How does the IDL’s zigzag shape help countries like Russia and the USA?

• The IDL bends around places like Russia’s eastern islands and Alaska to keep them on the same date as their mainlands. This avoids having parts of the same country on different days, which would complicate governance.

10. Why does the IDL matter for modern global transportation?

• The IDL ensures flights and ships adjust dates correctly, like a plane leaving Tokyo on Tuesday arriving in San Francisco on Monday. This coordination keeps worldwide schedules accurate and organized.