Question

5. Write out the steps of the Chapman cycle of ozone. Where is ultraviolet radiation involved? What does it mean when we say that ozone "absorbs" ultraviolet radiation? I

Answer 1

Solution: The continuous ozone-oxygen cycle that exists in the stratosphere is known as Chapman cycle. It is the process by which ozone is continually regenerated in the Earth's stratosphere, converting ultraviolet radiation into heat.

The steps involved in the Chapman cycle are as follows:

1) UV radiations of wavelength 120-210 nm strike the ordinary O2 molecules, which results in their bond cleavage. The oxygen molecules splits into two oxygen atoms.

2) These oxygen atoms collide with molecules of oxygen present in the atmosphere, which results in the formation of ozone (O3).

3) These ozone molecules absorbs a range of ultraviolet radiations and again split into one oxygen molecule and an oxygen atom.

4) These free oxygen atoms collide with molecules of ozone, resulting in the formation of two oxygen molecules.

Ozone "absorbs" ultraviolet radiation.

Ozone absorbs the ultraviolet radiations. There is so much oxygen present in our stratosphere that these high-energy ultraviolet radiations are completely absorbed in the stratosphere. Ozone is extremely valuable since it absorbs a range of ultraviolet energy. When an ozone molecule absorbs even low-energy ultraviolet radiation, it splits into an ordinary oxygen molecule and a free oxygen atom. Usually this free oxygen atom quickly re-joins with an oxygen molecule to form another ozone molecule. Because of this "ozone-oxygen cycle," harmful ultraviolet radiation is continuously converted into heat.