Select the correct statement about ozone :

Question

Accepted Answer

Explanation:

1. **Justification for Option 3: Ozone absorbs ultraviolet rays and forms oxygen**

Ozone (O₃) is a molecule composed of three oxygen atoms. It plays a crucial role in the Earth's atmosphere by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation. When ozone absorbs UV rays, it undergoes a photodissociation process, where the energy from the UV light breaks the ozone molecule into an oxygen molecule (O₂) and a single oxygen atom (O). This process is essential for protecting living organisms on Earth from the damaging effects of UV radiation, such as skin cancer and cataracts.

2. **Explanation of why the other options are incorrect:**

- **Option 1: The percentage of ozone in our atmosphere is 7.8%**

This statement is incorrect. Ozone constitutes only a very small fraction of the Earth's atmosphere. In fact, ozone makes up about 0.00006% of the atmosphere by volume. The 7.8% figure is vastly exaggerated and does not accurately represent the concentration of ozone.

- **Option 2: Tropospheric ozone is "good ozone"**

This statement is incorrect. Tropospheric ozone, which is found in the lowest part of the Earth's atmosphere, is actually considered "bad ozone." It is a major component of smog and can have harmful effects on human health, vegetation, and the environment. In contrast, stratospheric ozone, found in the upper atmosphere, is known as "good ozone" because it protects life on Earth by absorbing UV radiation.

- **Option 4: Ozone increases the amount of chloro-fluoro-carbons in the stratosphere**

This statement is incorrect. Ozone does not increase the amount of chlorofluorocarbons (CFCs) in the stratosphere. In fact, CFCs are human-made compounds that contribute to the depletion of the ozone layer. When CFCs reach the stratosphere, they release chlorine atoms upon exposure to UV radiation, which then react with ozone molecules, leading to ozone depletion. Therefore, ozone does not increase CFCs; rather, CFCs are responsible for reducing ozone levels.

In conclusion, Option 3 is the correct statement as it accurately describes the role of ozone in absorbing ultraviolet rays and forming oxygen, which is vital for protecting life on Earth.