**Major contributors to acid rain are SO2 and NO2**

***Explanation:***

**1. Acid Rain**
Acid rain refers to rainfall that has a pH value below 5.6, which is considered acidic. It is primarily caused by the emission of certain pollutants into the atmosphere, which then react with water vapor and other atmospheric components to form acidic compounds. These acidic compounds can then be deposited on the Earth's surface through precipitation, leading to harmful effects on the environment.

**2. Major Contributors**
The major contributors to acid rain are sulfur dioxide (SO2) and nitrogen dioxide (NO2). These gases are released into the atmosphere through human activities, particularly the burning of fossil fuels such as coal, oil, and gas.

**2.1 Sulfur Dioxide (SO2)**
Sulfur dioxide is primarily produced by the combustion of fossil fuels that contain sulfur compounds. It is released into the atmosphere from various sources, including power plants, factories, and vehicles. Sulfur dioxide can undergo chemical reactions in the atmosphere to form sulfuric acid (H2SO4), one of the main components of acid rain. These reactions occur through a series of oxidation reactions involving sulfur dioxide, oxygen, and water vapor.

**2.2 Nitrogen Dioxide (NO2)**
Nitrogen dioxide is primarily produced by the combustion of fossil fuels at high temperatures, such as in power plants, vehicles, and industrial processes. It is a major component of smog and contributes to the formation of acid rain. Nitrogen dioxide can react with water vapor and other atmospheric components to form nitric acid (HNO3), another key component of acid rain.

**3. Chemical Reactions**
In the atmosphere, sulfur dioxide and nitrogen dioxide undergo chemical reactions to form sulfuric acid and nitric acid, respectively. These acids can then combine with water vapor to form acidic solutions, which can be deposited on the Earth's surface through precipitation. The deposition of these acids can have detrimental effects on ecosystems, including the acidification of lakes, rivers, and soils, which can harm aquatic life and vegetation.

**4. Control Measures**
To mitigate the effects of acid rain, various control measures have been implemented. These include the installation of flue gas desulfurization systems in power plants to reduce sulfur dioxide emissions, the use of catalytic converters in vehicles to reduce nitrogen oxide emissions, and the promotion of cleaner energy sources such as renewable energy. These measures aim to reduce the emission of pollutants that contribute to acid rain and protect the environment from its harmful effects.

In conclusion, sulfur dioxide (SO2) and nitrogen dioxide (NO2) are the major contributors to acid rain. These gases are released into the atmosphere through human activities and undergo chemical reactions to form sulfuric acid and nitric acid, respectively, which can then be deposited on the Earth's surface through precipitation. Implementing control measures to reduce these emissions is crucial in mitigating the effects of acid rain on the environment.