Trace the step-by-step process by which UV radiation from the Sun leads to the formation of ozone in the upper atmosphere. How does the same UV radiation that is responsible for creating ozone also justify the need for an ozone layer? What would happen to life on Earth if this layer were to be significantly depleted?
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer
Formation of Ozone:
UV radiation from the Sun strikes oxygen molecules (O₂) in the upper atmosphere, splitting them into free oxygen atoms (O). These free atoms then combine with other O₂ molecules to form ozone (O₃):
$$O_2 \xrightarrow{\text{UV}} O + O$$
$$O + O_2 \rightarrow O_3$$
Need for Ozone Layer:
The same UV radiation that creates ozone is highly damaging to living organisms — it causes skin cancer in humans. Therefore, the ozone layer is essential as it shields Earth's surface from this harmful UV radiation.
Effect of Depletion:
If the ozone layer were significantly depleted, more UV radiation would reach Earth, causing increased skin cancer, genetic damage to organisms, and serious harm to ecosystems.
Source: Chapter 13, Section 13.2.1 — Ozone Layer and How it is Getting Depleted
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Explanation
- 3-mark structure: Examiners expect three clear points — (1) the chemical process of ozone formation with equations, (2) why UV itself justifies the need for the layer, and (3) consequences of depletion.
- Always write the two-step reaction — splitting of O₂ and then combination to form O₃ — as it is directly from the textbook.
- The key logical link examiners look for: UV creates ozone and UV is harmful → ozone layer blocks UV → life is protected. This "same radiation" connection is the heart of the question.
- Avoid writing irrelevant points about CFCs here; the question is specifically about UV and ozone formation/need.