When ultraviolet (UV) light strikes the ozone layer in Earth's atmosphere, which of the following occurs?

• A. Ozone molecules (O_3) absorb UV light and undergo decomposition into O_2 and O.
• B. Ozone molecules (O_3) are converted directly into water vapor.
• C. Ozone molecules (O_3) emit visible light as fluorescence.
• D. Ozone molecules (O_3) combine with nitrogen to form nitrogen oxides.

Answer: (A)

Verified step by step guidance

1. Understand the role of ozone (O_3) in the Earth's atmosphere, particularly in the stratosphere where it forms the ozone layer.
2. Recall that ozone absorbs ultraviolet (UV) light, which provides protection by preventing most UV radiation from reaching the Earth's surface.
3. Recognize that when ozone absorbs UV light, it undergoes a photochemical reaction where the O_3 molecule breaks down (decomposes) into molecular oxygen (O_2) and a single oxygen atom (O).
4. Note that this decomposition is a key part of the ozone-oxygen cycle, which helps regulate the concentration of ozone and oxygen in the atmosphere.
5. Conclude that the correct process is the absorption of UV light by ozone leading to its decomposition into O_2 and O, rather than conversion into water vapor, emission of visible light, or combination with nitrogen.