Why are the sun’s UV rays more harmful in the afternoon than in the morning or evening?

Question

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

Answer 1

Remember that there’s a layer of atmosphere between you and the sun. When the sun appears lower in the sky, it has a lot more air to go through to get to you. When directly overhead, the sun’s rays only have to travel through the air above you- the shortest journey or the thinnest filter.