Ozone hole refers to

Step 1: Analyze the question The question asks what "ozone hole" actually means. This is about the ozone layer and where it is found.

Step 2: Explain the concept

• The ozone layer is a region of the atmosphere with a high concentration of ozone (O₃). It is found in the stratosphere, roughly 15-35 km above the Earth.
• Its job is to absorb harmful ultraviolet (UV) radiation from the sun, which protects living things from skin cancer, cataracts and crop damage.
• Chemicals such as chlorofluorocarbons (CFCs), used in refrigerators, aerosol sprays and air conditioners, release chlorine in the stratosphere. The chlorine breaks down ozone molecules.
• The "ozone hole" is not a literal hole. It is an area where the ozone layer has become abnormally thin (depleted), most famously over Antarctica.

Step 3: Evaluate the options

• A. Hole in ozone layer: This sounds right, but it is a literal reading and merely repeats the term. It does not describe what is happening scientifically.
• B. Decrease in the ozone layer in troposphere: Wrong location. The protective ozone layer is in the stratosphere. Ozone in the troposphere is a pollutant.
• C. Decrease in thickness of ozone layer in stratosphere: Correct. It gives both the process (thinning) and the right location (stratosphere).
• D. Increase in thickness of ozone layer in troposphere: Wrong on both counts. The ozone hole is a decrease, not an increase, and the layer is not in the troposphere.

Step 4: Answer The ozone hole refers to the decrease in thickness of the ozone layer in the stratosphere, which is option C.

Exam tip: Remember "Stratosphere = Sunscreen". Ozone high up in the stratosphere shields us from UV rays. If an option mentions the troposphere for the ozone layer, you can eliminate it immediately. Also, be careful with options that just repeat the question's words, like A. JAMB usually prefers the scientifically precise description.