Question

why does the amount of sun light vary on latitude?

Answer 1

at 0 degree latitude (Equator) the sun rays falls straight but when we move towards north or south poles(increasing latitude) the sun's rays become slant. During the revolution of earth around the sun on 21 June sun's rays fall straight on tropic of cancer hence it is the longest day in northern hemisphere (summer solistic) and in 22 Dec sun's rays falls straight on tropic of Capricorn hence it is the longest day of southern hemisphere(winter solistic).