Q 2. 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

Ans: (a) East to West

(2) If it is Wednesday 10 a.m. at 150 E⁰ 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.

Ans: (b) Wednesday 9 p.m.

(3) According to the international convention, at which meridian does the day and date change occurs? 

(a) 0⁰

(b) 90⁰ E

(c) 90⁰ W 

(d) 180⁰

Ans: (d) 180°

(4) At which direction of the IDL does a new day start immediately?

(a) East 

(b) West 

(c) North 

(d) South

Ans: (b) West

(5) IDL brings coordination in which of the following?

(a) GPS system 

(b) Defence departments 

(c) Transportation schedules 

(d) Determining the hemisphere

Ans: (c) Transportation schedules 

Q 3. Give geographical reasons.

(1) IDL is proving to be very useful in today’s times.

Ans: IDL is proving to be very useful in today’s times because:

(i) The IDL brings coordination between international airlines, transportation services, and economic and trade activities.

(ii) The IDL has been carved out of the necessity of coordinating time and date.

(iii) It is also important in today’s modern era and in light of rapidly happening global developments.

(iv) We can keep track of all the calculations of a day and time accurately with the help of IDL in the case of global transportation, especially with respect to airways.

(v) It is only because of the IDL that the schedules of traffic worldwide are organised properly.

(2) The day starts in Pacific Ocean on the earth.

Ans:

(i) The IDL passes through the Pacific Ocean.

(ii) With reference to the IDL, the day on Earth starts in the west and ends in the east.

(iii) It is one and the same day only at 12 o’clock midnight at the 180° meridian.

(iv) For the countries lying to the east of it, i.e., the USA, Chile, etc., it is the end of the day, while for the countries lying to the west of it, i.e., Japan, Australia, etc., it is the start of a new day.

Thus, a new day starts in the Pacific Ocean on Earth.

Q 4. Write in brief:

(1) What considerations have been made while deciding the IDL?

Ans: The International Date Line is an imaginary line that was agreed upon by the countries of the world in 1884. When you cross the 180⁰ meridian, some precautions need to be taken as it can result in a change of time zone. According to the convention, the start and end of a date are considered to be at the 180⁰ meridian. The following points were taken into consideration while drawing the International Date Line (IDL):

(i) The direction of travel

(ii) The current day and date

(2) While crossing the IDL, what changes will you make?

Ans:

(i) While travelling from east to west along the IDL, one needs to add a day to the date. 

For example, while travelling from America to Japan, if it is Thursday, December 25th, then it will be Friday, December 26th in Japan.

(ii) While travelling from west to east of IDL, the day remains the same. 

For example, while travelling from Japan to America, only Thursday, December 25th, should be considered.

(3) Why is the IDL not a straight line like the 180⁰ meridian?

Ans:

(i) An attempt has been made to make the IDL pass through the Pacific Ocean completely.

(ii) People would have needed to observe different dates and timing if it had passed through a land mass or a few islands because the dates would have been different on their eastern and western sides.

(iii) Additionally, it would have been difficult to know when the date on the calendar changes and when one crosses the IDL on land.

(iv) Therefore, the IDL is not a straight line like the 180° Meridian, and it turns east while, at other places, it turns west, although the maximum part of the IDL coincides with the 180⁰ meridian.

(4) Why doesn’t the IDL pass through land? 

Ans:

(i) An attempt has been made to make the IDL pass through the Pacific Ocean completely.

(ii) People would have needed to observe different dates and timing if it had passed through a land mass or a few islands because the dates would have been different on their eastern and western sides.

(iii) Additionally, it would have been difficult to know when the date on the calendar changes and when one crosses the IDL on land.

(iv) Therefore, the IDL is not a straight line like the 180° Meridian, and it turns east while, at other places, it turns west, although the maximum part of the IDL coincides with the 180⁰ meridian.

(5) Why is the IDL considered with respect to the 180⁰ meridian only? 

Ans: Our 24-hour day starts at midnight. Because of the earth’s rotation, midnight occurs at different times and in different places. As the Earth is spherical in shape, every place has a place to its east. So, it was necessary to determine at what location on Earth, toward the east, the day starts. Hence, representatives of many nations got together under the leadership of an American professor, Davidson, in the year 1884 and decided the International Date Line. The line was drawn opposite to the Greenwich Prime Meridian, i.e., with reference to the 180° Meridian.

Q 5. 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 

Ans: IDL will be crossed.

(2) Delhi – Kolkata – Singapore – Melbourne 

Ans: IDL will not be crossed.

(3) Kolkata – Hong Kong – Tokyo – San Francisco

Ans: IDL will be crossed.

(4) Chennai – Singapore – Tokyo – Sydney – Santiago

Ans: IDL will be crossed.

(5) Delhi – London – New York

Ans: IDL will not be crossed.