Question

A line passing through 180° meridian which is diametrically opposite to the Greenwich line is adopted as _______________.
(A) Equator
(B) International Date Line
(C) Tropical lines
(D) Tropic of Cancer

Answer 1

Hint: It is an imaginary line stretching between the North Pole and the South Pole and demarcates each calendar day from the next. Following a 180 degrees longitude north-south line on the Earth, it passes through the mid-Pacific Ocean. From the prime meridian, it is located halfway around the world.

Complete answer: It is the International Date Line (IDL) that corresponds along to the 180° meridian of longitude and is opposite to the Greenwich line. Since it mostly runs through the less-populated Central Pacific Ocean, the 180° meridian was selected as the International Date Line. It was in the International Meridian Conference in 1884 in Washington, D.C. the decision to select 180° as IDL was taken. Separating two consecutive calendar dates, it acts as a line of demarcation. IDL functions as a consequence of the worldwide use of timekeeping systems arranged so that local noon corresponds nearly to the time at which the sun crosses the local meridian of longitude.
The Greenwich meridian acts as the basis for the standard time zone system in the world. The mean solar time at Greenwich is called as Universal Time. The prime meridian and the International Date Line marks a division of the Earth into the eastern and western hemispheres.

Option (A): Located at zero degrees latitude, the Equator is an imaginary line which is around the middle of Earth. This is incorrect.
Option (B): The International Date Line is the line passing through 180° meridian. This is the correct option.
Option (C): The lines where the sun is directly overhead at noon on the two solstices are tropical lines. This is incorrect.
Option (D): The Tropic of Cancer and the Tropic of Capricorn are the two tropics that lies at 23.5 degrees latitude. This is incorrect.

Thus the option (B) is correct.

Note: The east of the prime meridian and west of the International Date Line is the eastern hemisphere. Most of Earth's area, including all of Asia and Australia, and most of Africa, are in the eastern hemisphere. The western hemisphere is east of the International Date Line and west of the prime meridian. The landmasses in the western hemisphere comprise the Americas, the western part of the British Isles and the northwestern part of Africa.