Amount of Insolation received at earth's equator is 100 percent and at poles it is:

Question

Accepted Answer

The amount of insolation received at the Earth's equator is significantly higher than at the poles due to several factors. Option 1, stating that the poles receive 42 percent of the insolation received at the equator, is the correct answer. Here's why:

*   **Angle of Incidence:** The primary reason for the difference in insolation is the angle at which sunlight strikes the Earth's surface. At the equator, the sun's rays strike the surface at a near-perpendicular angle (close to 90 degrees). This means the energy is concentrated over a smaller area, resulting in higher insolation. At the poles, the sun's rays strike at a much more oblique angle. This spreads the same amount of energy over a larger area, reducing the intensity of insolation. The lower angle of incidence at the poles is a key factor in the 42% figure.

*   **Atmospheric Absorption and Scattering:** Sunlight travels through more of the atmosphere to reach the poles than it does to reach the equator. This longer path length increases the amount of solar radiation that is absorbed, scattered, and reflected back into space by atmospheric particles (like clouds, dust, and gases). This further reduces the amount of insolation that reaches the surface at the poles, contributing to the 42% figure.

*   **Earth's Curvature:** The curvature of the Earth is the fundamental reason for the varying angle of incidence. Because the Earth is a sphere, the angle at which sunlight strikes the surface changes with latitude. This is the underlying cause of the difference in insolation between the equator and the poles, and it supports the 42% figure.

Now, let's explain why the other options are incorrect:

*   **Option 2: 47 Percent:** While the poles do receive some insolation, 47% is an overestimate. The combined effects of the angle of incidence and atmospheric absorption significantly reduce the amount of solar radiation reaching the poles to a level lower than 47% of the equatorial insolation.

*   **Option 3: 57 Percent:** This percentage is even further from the actual amount of insolation received at the poles. The factors mentioned above (angle of incidence, atmospheric absorption) make it impossible for the poles to receive this much insolation relative to the equator.

*   **Option 4: 32 Percent:** While this is closer to the correct answer than options 2 and 3, it's still an underestimate. The poles do receive some solar radiation, and 32% is too low to account for the amount that actually reaches the surface, even considering the oblique angle and atmospheric effects.

In conclusion, the combination of the angle of incidence, atmospheric absorption, and the Earth's curvature results in the poles receiving significantly less insolation than the equator. Option 1, stating 42 percent, is the correct answer because it best reflects the actual proportion of insolation received at the poles compared to the equator.