Which parts of the earth's surface experience least variation in in- coming solar rad inti tin through- out the year ?

The equatorial regions experience the least variation in incoming solar radiation (insolation) throughout the year. This consistency is primarily due to the Earth's spherical shape and axial tilt, which ensure that the sun's rays hit the equator almost perpendicularly year-round [4]. Near the equator, the amount of solar radiation remains relatively constant, leading to minimal seasonal temperature fluctuations [2]. In contrast, higher latitudes, particularly the polar regions, experience extreme variations in insolation due to the dramatic changes in day length and the angle of inclination of the sun's rays as the Earth orbits the sun [3]. While the tropics (Cancer and Capricorn) receive high total insolation, they experience more pronounced seasonal shifts than the equator because the subsolar point migrates between them. Consequently, the equatorial belt maintains the most stable radiation receipt across all seasons.

Sources

1. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Variation in the Net Heat Budget at the Earth's Surface > p. 70
2. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Variability of Insolation at the Surface of the Earth > p. 67
3. [1] https://www.khanacademy.org/science/ap-college-environmental-science/x0b0e430a38ebd23f:earth-systems-and-resources/x0b0e430a38ebd23f:earths-seasons/a/solar-radiation-and-earths-seasons
4. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Spatial Distribution of Insolation at the Earth's Surface > p. 68