Questions Answers For All Chapters – Geography Class 9th
Exercise
Q1. Two boxes in different hemispheres are given in the following diagram. The IDL passes through both the boxes. In one box, the meridian, day, and date is given. Find the day and date for the other box.
- Assumption: Box A (East of IDL) is 180°, Monday, 1st January.
- Answer for Box B (West of IDL): Box B is Tuesday, 2nd January.
- Reason: When crossing the IDL from east to west, you add one day.
Q2. Select the correct option:
(1) While crossing the IDL, a person will have to add one day when travelling from
- (a) East to West
- (b) West to East
- (c) South to North
- (d) North to South
Answer: (a) East to West
Reason: Crossing from east to west over the IDL adds a day (e.g., Monday becomes Tuesday).
(2) If it is Wednesday 10 a.m. at 15° E meridian, then what will be the time at IDL?
- (a) Wednesday 6 a.m.
- (b) Wednesday 9 p.m.
- (c) Thursday 2 p.m.
- (d) Thursday 6 p.m.
Answer: (b) Wednesday 9 p.m.
Reason: 15° E to 180° (IDL) is 165° east; each 15° is 1 hour ahead, so 165° ÷ 15 = 11 hours ahead of 10 a.m., which is 9 p.m. on Wednesday.
(3) According to the international convention, at which meridian does the day and date change occur?
- (a) 0°
- (b) 90° E
- (c) 90° W
- (d) 180°
Answer: (d) 180°
Reason: The 180° meridian is where the IDL is based, and the day changes when crossing it.
(4) At which direction of the IDL does a new day start immediately?
- (a) East
- (b) West
- (c) North
- (d) South
Answer: (b) West
Reason: A new day starts west of the IDL (e.g., Japan) as Earth rotates west to east.
(5) IDL brings coordination in which of the following?
- (a) GPS system
- (b) Defence departments
- (c) Transportation schedules
- (d) Determining the hemisphere
- Answer: (c) Transportation schedules
- Reason: The IDL helps organize airline and shipping schedules worldwide by tracking dates and times.
Q3. Give geographical reasons.
(1) IDL is proving to be very useful in today’s times.
- The IDL helps airlines and ships keep accurate schedules across the world.
- It prevents confusion in trade and travel by setting a clear date change line.
(2) The day starts in the Pacific Ocean on the Earth.
- The IDL runs through the Pacific Ocean, and west of it (e.g., Japan) gets the new day first.
- Earth rotates west to east, so the western side of the IDL starts the day earlier.
Q4. Write in brief:
(1) What considerations have been made while deciding the IDL?
- Direction of travel: East to west adds a day, west to east subtracts a day.
- Current day and date: These are adjusted when crossing the 180° meridian.
(2) While crossing the IDL, what changes will you make?
- From east to west, add one day (e.g., Monday becomes Tuesday).
- From west to east, subtract one day (e.g., Tuesday becomes Monday).
(3) Why is the IDL not a straight line like the 180° meridian?
- The IDL bends to avoid splitting islands and countries with different dates.
- It stays mostly in the Pacific Ocean to keep land areas on the same day.
(4) Why doesn’t the IDL pass through land?
- If it passed through land, people on either side would have different dates, causing confusion.
- It’s kept in the ocean to make date changes clear for travelers.
(5) Why is the IDL considered with respect to the 180° meridian only?
- The 180° meridian is opposite the 0° Greenwich meridian, making it a natural date change point.
- It was chosen in 1884 by international agreement for global time coordination.
Q5. Using an atlas, tell in which of the following routes the IDL will be crossed and show them on the map.
(1) Mumbai – London – New York – Los Angeles – Tokyo
- Yes, IDL crossed: Between Los Angeles (east of IDL) and Tokyo (west of IDL).
(2) Delhi – Kolkata – Singapore – Melbourne
- No, IDL not crossed: All locations are west of the IDL in the Eastern Hemisphere.
(3) Kolkata – Hong Kong – Tokyo – San Francisco
- Yes, IDL crossed: Between Tokyo (west of IDL) and San Francisco (east of IDL).
(4) Chennai – Singapore – Tokyo – Sydney – Santiago
- Yes, IDL crossed: Between Tokyo (west of IDL) and Santiago (east of IDL via Sydney).
(5) Delhi – London – New York
- No, IDL not crossed: All locations are east of the IDL in the Western Hemisphere.
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