The following is true about ozone :

Question

Accepted Answer

Ozone is a molecule composed of three oxygen atoms, and it plays a crucial role in the Earth's atmosphere. Let's examine why Option 2 is the correct answer and why the other options are incorrect:

1. **Option 2: It absorbs ultraviolet rays.**  
   This statement is correct. Ozone is primarily found in the Earth's stratosphere, forming the ozone layer. This layer is essential because it absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, particularly UV-B and UV-C rays. By absorbing these rays, the ozone layer protects living organisms on Earth from potential damage, such as skin cancer and cataracts in humans, and harmful effects on animals and plants.

2. **Option 1: It is essential for respiration of animals and plants.**  
   This statement is incorrect. Ozone is not essential for respiration. In fact, ozone at ground level is considered a pollutant and can be harmful to both animals and plants. The gas that is essential for respiration is oxygen (O2), not ozone (O3).

3. **Option 3: Its percentage in air is almost 3%.**  
   This statement is incorrect. Ozone makes up a very small fraction of the Earth's atmosphere. The concentration of ozone in the atmosphere is much less than 3%. In fact, it is only present in trace amounts, with the highest concentrations found in the ozone layer of the stratosphere.

4. **Option 4: It is used to disinfect water.**  
   While ozone can be used to disinfect water due to its strong oxidizing properties, this is not its primary or most significant role in the context of the Earth's atmosphere. The question focuses on the atmospheric role of ozone, where its ability to absorb ultraviolet rays is of paramount importance.

In summary, Option 2 is the correct answer because the most significant and well-known role of ozone in the Earth's atmosphere is its ability to absorb ultraviolet rays, thereby protecting life on Earth from harmful solar radiation.