Why does distance from the equator cause uneven sun energy distribution?

Why does distance from the equator cause uneven sun energy distribution?

• A. The Sun's energy is strongest at the equator and weaker at higher latitudes.
• B. The atmosphere blocks solar energy equally at all latitudes.
• C. The angle of solar incidence is shallower at higher latitudes, spreading energy over a larger area.
• D. There is no variation in distribution with latitude.

Answer: (C)

Sunlight energy is the same in total, but how it is spread on the Earth's surface depends on the angle at which the rays hit. Near the equator the sun is high in the sky, so rays strike almost perpendicularly and concentrate on a smaller patch of ground, delivering more energy per square meter. As you move toward higher latitudes, the sun sits lower, and rays arrive at a shallower angle. Those same rays then fan out over a larger area, reducing the energy per unit area that reaches the surface. In mathematical terms, irradiance on a surface scales with the cosine of the solar zenith angle, which decreases as you go toward the poles. The atmosphere also adds some attenuation for oblique rays, but the key idea is the slower, more oblique incidence at higher latitudes spreads energy over a larger area, causing uneven distribution.

Sunlight energy is the same in total, but how it is spread on the Earth's surface depends on the angle at which the rays hit. Near the equator the sun is high in the sky, so rays strike almost perpendicularly and concentrate on a smaller patch of ground, delivering more energy per square meter. As you move toward higher latitudes, the sun sits lower, and rays arrive at a shallower angle. Those same rays then fan out over a larger area, reducing the energy per unit area that reaches the surface. In mathematical terms, irradiance on a surface scales with the cosine of the solar zenith angle, which decreases as you go toward the poles. The atmosphere also adds some attenuation for oblique rays, but the key idea is the slower, more oblique incidence at higher latitudes spreads energy over a larger area, causing uneven distribution.