Question

Which area of the Earth receives maximum sunlight?
A) Polar region
B) Equatorial region
C) Along the latitude of tropic of cancer
D) Along the latitude of tropic of Capricorn

Answer 1

Hint: Polar regions start from the point where the axis line of the Earth’s rotation passes through. The Equatorial region lies between the lines- tropic of cancer and tropic of Capricorn, this also contains the equator line which lies in the center of the earth and directly faces the sun. The region along the tropic of cancer stretches up to the arctic circle, while the region along the tropic of capricorn stretches up to the Antarctic circle.

Complete step by step solution:
This diagram will give a better understanding of the concept.
 

When the Earth revolves around the Sun, It creates a slightly elliptical orbit like this-
 

All around the year, the Earth is ${23.5}^{\circ }$ inclined from vertical relative to this plane.
The earth’s surface is divided into a number of parallel, horizontal, imaginary lines called Latitudes. The location of latitude is specified using the angle which it makes with the central latitude called the Equator line, it is marked as $0^{\circ }$.
Due to the curved spherical surface of the Earth, the amount of sunlight that reaches a particular latitude is proportional to its cosine.
$I\propto \cos \theta$
Where I is the amount of sun’s light that reaches the area.
And $\theta$ represents the latitude.
This can be useful to calculate the share of sunlight in each area.
Since, $\cos 0^{\circ }=1$, sunlight is maximum at the equator.
And, $\cos {90}^{\circ }=0$, sunlight is minimum at the poles.
So moving from the equator to the poles we find a decrease in the amount of sunlight that falls on earth.

The earth has 3 types of zones-
1. The equatorial zone- Lies between the tropic of cancer (${23}^{\circ }{26}^{\prime }N$) and the tropic of Capricorn (${23}^{\circ }{26}^{\prime }S$).
2. The temperate zone- Lies between the tropic of cancer (${23}^{\circ }{26}^{\prime }N$ ) and arctic circle (${66}^{\circ }{34}^{\prime }N$); and between the tropic of Capricorn (${23}^{\circ }{26}^{\prime }S$) and Antarctic circle (${66}^{\circ }{34}^{\prime }S$).
3. The polar region- Lies between the arctic circle (${66}^{\circ }{34}^{\prime }N$) and the north pole (${90}^{\circ }N$); and between the Antarctic circle (${66}^{\circ }{34}^{\prime }S$) and the south pole (${90}^{\circ }S$).

Since $\cos \theta$ is maximum around the equatorial region, it receives maximum sunlight. Option (B) is correct.

Note: Even if the earth’s axis is inclined, the portion of the Earth which receives maximum sunlight remains on the Equatorial region, because the tropic of cancer and the Capricorn, which act as a borderline between temperate and equatorial region is placed at around ${23.5}^{\circ }$, which is the maximum distance which can be reached by equatorial region, which cancels out the inclination of the earth.