I always hear that we should avoid the sun or make sure to put on sunscreen in the afternoon when the sun is the most intense. Why is the sun’s rays more harmful when it is directly overhead vs in the morning soon after sunrise? Either way, the sun is shining directly on me so not sure what causes the difference in intensity.
In: Planetary Science
Imagine you point a flashlight directly at a globe with the flashlight even with the equator. The globe is surrounded by a layer of atmosphere made of gasses and other particles like dust in the air, which blocks/scatters some of the light.
The light that hits the equator is traveling a shorter distance to reach the surface because the round globe bulges most at the middle, and that light is taking a direct route through the atmosphere to reach the surface. This is the path of last resistance.
If you look further up/down the globe, the surface curves away from the flashlight. The light must to travel further to reach the surface and it must pass through more atmosphere because of its angle. More light is blocked/scattered this way, which is what reduces the intensity of the UV rays that reach us.
This is a simplified and slightly altered version of reality, but the concept for UV index is the same.
Latest Answers