Question

The time lag from Gujarat to Arunachal Pradesh is of
(A) 2 hrs. 45 min
(B) 2 hrs.
(C) 50 min
(D) 3 hrs.

Answer 1

Hint: Pole experience midday or noon at the same time. However, every longitude experiences noon at a different time. Thus, it would be right to say that local time varies from one longitude to another.

Complete Answer:
The Earth takes twenty four hours to cover three sixty degrees of longitudes, i.e., one rotation. So in our hour it covers fifteen degrees of longitudes and in four minutes it covers one degree of longitude. This means there is a difference of four minutes between the local times of any two longitude that are one degree apart.
India covers thirty degrees of longitude, therefore there is a difference of two hours between the local time of the westernmost state and the easternmost state.
Gujarat is a westernmost state and Arunachal Pradesh is a easternmost state.
There is a four minute difference between the longitudes that are one degree apart. The difference between the longitude of Gujarat and Arunachal Pradesh is thirty degrees. Hence the time lag from Gujarat to Arunachal Pradesh is two hours.

So the correct answer is (B).

Additional Information:
Due to the difference of time between longitude, it becomes essential to follow a common time throughout the country. Thus 8230’E was chosen as the standard meridian of India. The local time of meridian is called Indian Standard Time(IST) and is followed throughout India.

Note: The local time of the Prime Meridian is called Greenwich Mean Time (GMT). It is the Standard Time for the UK. Often, the standard times in different countries are expressed as a difference in the number of hours from the GMT. The IST is five and a half hours ahead of GMT. This means that when it is four pm in the UK, it is 9:30pm in India.