📚 Part of: Indian Geography And History Mcq Quiz

If the local time at Dwarka (69$^\circ$01'E) in Gujarat to the west of India is 6 am, what will be the local time at Dibrugarh (94$^\circ$58'E approximately 95$^\circ$), in Assam, in the east?

Category: Miscellaneous Indian Gk

Correct Answer: C) 7:44 am.

Exam Relevance: UPSC Civil Services, SSC CGL, Bank PO, Railway Exams

Difficulty: Moderate

Concept notes:

India spans a wide range of longitudes, from approximately 68°E to 97°E. The standard time in India is based on the longitude of 82.5°E, which passes through the city of Allahabad. However, for local time calculations, the difference in longitude between two points is used to determine the time difference. Each degree of longitude corresponds to 4 minutes of time difference.

Common Mistakes:
  • Students often forget to convert the longitude difference into time difference correctly.
  • Some students might confuse the direction of time addition or subtraction based on the location's position relative to the reference point.
  • Students may not account for the exact minutes when converting degrees to time.
Explanation:

To understand the concept of local time differences in India, it is essential to consider the geographical spread of the country. India spans a wide range of longitudes, from approximately 68°E to 97°E. The standard time in India is based on the longitude of 82.5°E, which passes through the city of Allahabad. However, for local time calculations, the difference in longitude between two points is used to determine the time difference.

Each degree of longitude corresponds to 4 minutes of time difference. This is because the Earth rotates 360 degrees in 24 hours, which means it rotates 15 degrees per hour (360° / 24 hours = 15° per hour). Since there are 60 minutes in an hour, each degree of longitude corresponds to 4 minutes of time difference (60 minutes / 15 degrees = 4 minutes per degree).

In this problem, we are given the local time at Dwarka (69°01'E) and need to find the local time at Dibrugarh (95°E). The longitude difference between Dwarka and Dibrugarh is approximately 26 degrees (95° - 69°01' ≈ 26°). Since each degree of longitude corresponds to 4 minutes of time difference, the total time difference is 26 * 4 = 104 minutes, or 1 hour and 44 minutes.

Therefore, if it is 6 am in Dwarka, it will be 6 am + 1 hour and 44 minutes = 7:44 am in Dibrugarh. This calculation is based on the principle that time increases as we move eastward and decreases as we move westward. Since Dibrugarh is east of Dwarka, the time in Dibrugarh is later than the time in Dwarka.

It is important to note that this calculation assumes that both locations are on the same latitude and that the Earth's rotation is uniform. In reality, the Earth's rotation is not perfectly uniform, and there can be slight variations in the time difference due to factors such as the Earth's elliptical orbit and the tilt of its axis. However, for practical purposes, the calculation based on the longitude difference is sufficiently accurate for most applications.

In summary, the local time at Dibrugarh is 7:44 am when the local time at Dwarka is 6 am, based on the longitude difference and the principle that each degree of longitude corresponds to 4 minutes of time difference.

Option Analysis:
  • Option A: This option is incorrect. The time difference between Dwarka and Dibrugarh is more than 1 hour and 44 minutes, so 4:16 am is too early. The time difference is calculated based on the longitude difference, and each degree of longitude corresponds to 4 minutes of time difference.
  • Option B: This option is incorrect. The local time at Dibrugarh cannot be the same as Dwarka since they are at different longitudes. The time difference between the two locations is significant and must be accounted for.
  • Option C: This option is correct. The time difference between Dwarka (69°01'E) and Dibrugarh (95°E) is approximately 26 degrees. Since each degree of longitude corresponds to 4 minutes of time difference, the total time difference is 26 * 4 = 104 minutes, or 1 hour and 44 minutes. Therefore, if it is 6 am in Dwarka, it will be 7:44 am in Dibrugarh.
  • Option D: This option is incorrect. The time difference between Dwarka and Dibrugarh is less than 12 hours, so the time cannot be in the evening. The time difference is based on the longitude difference, and each degree of longitude corresponds to 4 minutes of time difference.

Mnemonic: Remember: "East adds, West subtracts" for time differences.

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