MP Board · Class 9 · Social Science · India - Size and LocationWhy is 82°30' E chosen as the Standard Meridian of India? Calculate the time difference between the easternmost and westernmost points of India based on their longitudes.

Step-by-step Calculation of Time Difference:

1. Longitudinal Extent of India:

   • Westernmost longitude (Gujarat) = 68°7' E
   • Easternmost longitude (Arunachal Pradesh) = 97°25' E
   • Longitudinal difference = 97°25' - 68°7' ≈ 30° (approx.)

2. Time Calculation:

   • Time taken by the Earth to rotate through 1° longitude = 4 minutes.
   • Total time difference for 30° = 30 × 4 minutes = 120 minutes = 2 hours.

Reason for selecting 82°30' E as Standard Meridian:\nDue to the broad longitudinal extent of nearly 30°, there is a time lag of about two hours between Gujarat in the west and Arunachal Pradesh in the east. If every region followed its local time, it would create immense confusion in railway schedules, air transport, and national communication. \nTo establish a uniform time throughout the country, a central meridian was required. The meridian of 82°30' E passing through Mirzapur in Uttar Pradesh was chosen as the Standard Meridian of India because:

• It passes almost through the middle of the country, dividing the longitudinal extent evenly.
• It is a multiple of 7°30' (which corresponds to a 30-minute time interval), following international conventions.