Is UV radiation filtered out by the ozone layer?

Answer 1

Short answer:

Yes, the ozone layer filters out all the UV-C (the most dangerous ultra-violet radiation) and most of the UV-B. The least dangerous radiation is UV-A, and most of this reaches the surface of the earth.

More detail:

Oxygen and nitrogen are the primary absorbers of UV-C and more energetic light (X-rays, gamma rays from space), and they do this completely by the lower stratosphere. One side effect of their absorption of this light, is they make ozone. This ozone is concentrated here, since it is unstable, and the "ozone layer" is formed. Some recombines into N2O*, which later forms either ozone or more stable NOx (if it encounters water vapor first). Some single oxygen atoms encounter O2 and make ozone directly.

Ozone absorbs UV light shorter than 260 nm or so. This includes UV-B, UV-C and more energetic light. Only ozone in our atmosphere absorbs UV-B, which would otherwise be stopped only by soil, meters depth of water, or the DNA of all surface life on Earth.

Additionally, the natural and Man-made "greenhouse gases" in our atmosphere (carbon dioxide, water vapor, ozone, for examples), serve to allow visible light and UV-A in to Earth's surface, but moderate the transmission of infrared light back to space... keeping Earth a tad bit warmer than it would otherwise be without an atmosphere.

Long wave UV (UV-A) and visible light always gets through the ozone layer. As the ozone layer is thinned, additional energetic UV (UV-B) gets through, which will cause problems down here on the surface.

As UV is absorbed, and used in a reaction O3 + uv light = O + O2 ,

Ozone directly absorbs UV-B and either becomes oxygen, or becomes ozone again, with the light scattered again in random directions.

When UV hits the Ozone (O3) it is 'absorbed,' meaning the energy is used to split the ozone into Oxygen gas (O2) and an Oxygen free radical (O). The remaining energy from the UV light is re-emitted as infra-red (heat).

O3 + UV-B -> O2 + O

The Ozone layer is situated on the upper stratosphere. Ozone (O3) is very unstable gas. Ozone is the only gas in our atmosphere that absorbs UV-B.

Oxygen and nitrogen molecules absorb UV-C and more energetic light, and later recombine in different forms. Oxygen atoms sometimes recombine to form ozone, and this primarily occurs in the lower stratosphere... and forms the ozone layer.

Oxygen and nitrogen protect us from very short wave UV, by absorbing the light and breaking apart.

Similarly, ozone has an extra resonance (than its parent oxygen), and can absorb less energetic UV, stuff that still causes cancer, and ozone breaks apart into oxygen gas and a oxygen atom looking for a place to land.

Infrared radiation such as the sun which is blocked by the ozone layer. Such as why to much time in the sun will give you skin cancer. Also it reminds you of when you go to the dentist, whoever is taking your x-ray never stays in the same room and that is why they put a huge metal pad over you. If they did not, it might give them cancer.

Oxygen and nitrogen absorb UV-C. Some of the "shattered" oxygen forms ozone. The UV-C mostly ends up as both heat, and re-emitted as less energetic light in a random direction.

Ozone absorbs UV-B (and some UV-C). The UV-B mostly ends up as heat, and re-emitted as less energetic light in a random direction. Some of the ozone is destroyed in the process of absorbing UV-C or UV-B, and little of it reforms as ozone.

Since atmospheric gases have very low absorptivity / emissivity at visible and IR wavelengths, they do not contribute to heating the surface of the Earth to any great extent. Ozone does have some limited resonance in the IR range, which is why it is called a greenhouse gas too. But it has very low concentration.

UV- C is filtered out but UV-A and UV-B however are not. UV-B is the radiation which begins oxidization of your skin and UV-A is the rays in which change the pigmentation of your skin togive you a tan, UV-C is the only extremely harmful rays and the ozone layer does in fact block them out.

Answer 2

No, they are not. The UV rays are not completely filtered out.