Consider the following places of India : 1. Itanagar 2. Imphal 3. Agartala 4. Aizawl Which one of the following is the correct chronological order of the above places in terms of sunrise time?
- (a)3–2–1–4
- (b)2–1–4–3
- (c)1–4–3–2
- (d)4–3–2–1
Correct — B, 2–1–4–3. The Earth turns from west to east, so the Sun rises first over whichever place lies furthest east, and the order of sunrise is simply the order of longitude read from east to west. The four capitals stand at roughly these longitudes: Imphal 93°56′ E, Itanagar 93°37′ E, Aizawl 92°43′ E and Agartala 91°17′ E. Reading from the easternmost westwards gives Imphal, Itanagar, Aizawl, Agartala — item 2, then 1, then 4, then 3. All four lie in the north-east within about three and a half degrees of latitude of one another, so latitude shifts sunrise only slightly and longitude decides the sequence.
- (a)3–2–1–4 — Opens with Agartala, which is the westernmost of the four at about 91°17′ E and therefore sees the Sun last, not first. This is the sequence a student picks who ranks the places west to east instead of east to west.
- (c)1–4–3–2 — Puts Itanagar first. Itanagar is far north, which makes it feel like the obvious answer, but at about 93°37′ E it lies a fraction of a degree west of Imphal at 93°56′ E, so Imphal catches the Sun a little earlier. The option then places Agartala ahead of Imphal, which reverses the two extremes.
- (d)4–3–2–1 — Gives Aizawl, Agartala, Imphal, Itanagar, which follows neither longitude nor latitude — it is the numbered list simply reversed.
The Earth completes one rotation of 360° in 24 hours, so it turns 15° of longitude in an hour and 1° in about four minutes. A place one degree east of another therefore sees sunrise about four minutes earlier on the same day. India spans roughly 68°7′ E to 97°25′ E, close to 30° of longitude, which is about two hours of sun time, yet the whole country keeps a single clock — Indian Standard Time, set to the 82°30′ E meridian that passes near Mirzapur in Uttar Pradesh.
Two things make this item harder than it looks. The first is that the four places are all in the north-east and their longitudes are close together, so a rough mental map is not enough — Imphal and Itanagar are separated by about a third of a degree, roughly a minute and a half of time. The second is the pull of latitude: Itanagar is much further north than the other three, and a student who reasons 'north-east means earliest' rather than 'east means earliest' will put it first. Fix a mental east-to-west order for the north-eastern capitals and the whole family of questions becomes answerable. Latitude and season do shift sunrise as well, but for places at similar latitudes on the same day, longitude decides who sees it first.
- The Earth rotates west to east, so eastern places see sunrise earlier.
- It turns 15° of longitude per hour, making 1° of longitude worth about four minutes of time.
- The approximate longitudes are Imphal 93°56′ E, Itanagar 93°37′ E, Aizawl 92°43′ E and Agartala 91°17′ E.
- Indian Standard Time is set to 82°30′ E, so the Sun rises about two hours earlier in eastern Arunachal Pradesh than in western Gujarat, though both keep the same clock.
- Latitude and the time of year also affect sunrise time, but among places at similar latitudes on the same day, longitude governs the order.
- Imphal, about 93°56′ E — first light (item 2)
- Itanagar, about 93°37′ E (item 1)
- Aizawl, about 92°43′ E (item 4)
- Agartala, about 91°17′ E — last (item 3)
Reading the four capitals from east to west gives 2–1–4–3, option (b).
- Ranking the places by latitude, or by a vague sense of which is 'more north-east', instead of by longitude.
- Reading the sequence west to east when the question asks for the order of sunrise.
- Assuming the north-eastern states share a time zone of their own; the whole of India keeps IST.
NDA regularly gives four Indian places and asks for their order by sunrise, by longitude or by latitude — the same question in three costumes, all answered from a mental map.
Along which one of the following meridians did India experience the first light of the sunrise of the new millennium?
- (a) 2° 30′ W
- (b) 82° 30′ E
- (c) 92° 30′ W
- (d) 92° 30′ E
Answer(d) 92° 30′ E
The same principle in a single step — the first sunrise falls on the easternmost meridian, which is exactly the rule that orders the four capitals here.
Sunrise in eastern Arunachal Pradesh would be about how many hours before the sunrise in western Gujarat ?
- (a) One hour
- (b) Two hours
- (c) Three hours
- (d) Four hours
Answer(b) Two hours
Puts a number on the same rule across the whole country, which is the arithmetic that makes the small gaps between these four capitals meaningful.
- practice — not a real PYQ
Two places in India lie on the same latitude but 5° apart in longitude. The difference in their local sunrise times is about
- (a)5 minutes
- (b)20 minutes
- (c)1 hour
- (d)5 hours
Answer(b) 20 minutes — the Earth turns 1° of longitude in about four minutes, so 5° corresponds to roughly twenty minutes.
- practice — not a real PYQ
Indian Standard Time is based on the meridian of
- (a)68°7′ E
- (b)77°0′ E
- (c)82°30′ E
- (d)97°25′ E
Answer(c) 82°30′ E — the meridian passing near Mirzapur in Uttar Pradesh, chosen as roughly central to India's longitudinal extent.