While the sun rises earlier in the east, say Nagaland and also sets earlier, how do the watches at Kohima and New Delhi show the same time?
India has a longitudinal variation of nearly 30 degrees, which causes a time difference of nearly two hours between the easternmost and westernmost parts of the country. Therefore, the sun rises earlier in the eastern states like Nagaland compared to places in the west.
To overcome this difference and maintain uniformity across the nation, India follows a single Indian Standard Time (IST). The standard meridian selected for this is 82°30' E. Since the entire country follows the time of this central meridian, the watches at Kohima in the east and New Delhi in the west show the same time.
Explanation
The textbook context explains that while there is a real time difference of nearly two hours from east to west due to the longitudinal extent, the concept of Indian Standard Time (IST) is used to maintain uniformity. The standard meridian (82°30' E) is chosen as the reference for time across the country, ensuring that all regions, regardless of local solar time, follow the same standard time.