Explanation:

While revolving around Sun, the earth's axis always remains inclined to one side. Because of this constant inclination in one direction, the Northern Hemisphere remains inclined towards the sun or faces the sun during one half of the year. Therefore, a larger part of this hemisphere receives sunlight. Every point in this hemisphere takes a longer time to go out of the sunlight, with the result that the days are longer. In contrast, the Southern Hemisphere is away from the sun. It, therefore, has shorter days and longer nights. During the other half of the year, the Southern Hemisphere is inclined towards the sun. Hence, it has longer days and shorter nights.