The correct option is (c) 1 and 3 only.
Explanation
The Standard Meridian of India is the specific longitude used to determine the Indian Standard Time (IST) for the entire nation. It is selected to pass through the approximate center of the country's longitudinal extent to harmonize the time difference between the western and eastern extremities.
Statement-wise Analysis
- Statement 1 is Correct: The longitude 82°30'E is officially designated as the Standard Meridian of India. This specific meridian was chosen because it is divisible by 7°30', a standard convention for time zones, allowing for a half-hourly difference from Greenwich Mean Time (GMT).
- Statement 2 is Incorrect: The Standard Meridian does not pass through Mumbai. It passes through Mirzapur (near Prayagraj/Allahabad) in Uttar Pradesh. Geographically, the line traverses five states: Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Odisha, and Andhra Pradesh. Mumbai is located significantly to the west, at approximately 72°50'E longitude.
- Statement 3 is Correct: India has a vast longitudinal extent of approximately 30 degrees. This creates a time difference of roughly two hours between the easternmost point (Arunachal Pradesh) and the westernmost point (Gujarat). To prevent administrative and logistical confusion caused by different local times, the time along the Standard Meridian is adopted as the uniform time for the whole country.
Key Takeaway
Indian Standard Time (IST) is based on the 82°30'E longitude, which passes through Mirzapur. It is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT) and serves to unify the time across India's two-hour longitudinal gap.