Science — CBSE Class 10 board question

Depletion of Ozone Layer:
Ozone layer at the higher levels of the atmosphere is getting depleted due to synthetic chemicals called chlorofluorocarbons (CFCs), which are used as refrigerants and in fire extinguishers. These chemicals react with ozone molecules and break them down, reducing the concentration of ozone in the atmosphere. This decrease was noted sharply in the 1980s.

One Harmful Effect:
Depletion of the ozone layer allows more ultraviolet (UV) radiation from the Sun to reach the Earth's surface. This UV radiation is highly damaging to organisms — for example, it causes skin cancer in human beings.

Source: Chapter 13, Section 13.2.1 — Ozone Layer and How it is Getting Depleted

---

• The 1-mark part is the cause (CFCs depleting ozone) — one crisp sentence suffices.
• The 2-mark part is the harmful effect — name UV radiation AND a specific consequence (skin cancer) for full marks. Just saying "UV rays increase" without a consequence loses a mark.
• Always name the chemical (CFC) in the cause; vague answers like "pollution" won't score.
• No need to write the chemical equations unless specifically asked.