Environmental Protection Agency (EPA) MVAC Certification

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Study for the EPA MVAC Certification. Dive into key environmental regulations with multiple choice questions, hints, and detailed explanations. Get ready to excel on your exam!

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What molecule is struck by UV light to create ozone in the Earth stratosphere?

  1. Hydrogen

  2. Nitrogen

  3. Oxygen

  4. Carbon Dioxide

The correct answer is: Oxygen

The formation of ozone in the Earth's stratosphere primarily involves the interaction between ultraviolet (UV) light and oxygen molecules. When UV light strikes oxygen (O₂) molecules, it causes them to dissociate into individual oxygen atoms. These free oxygen atoms can then react with other intact oxygen molecules to form ozone (O₃). This process is critical for the ozone layer, which absorbs the majority of the sun's harmful UV radiation, protecting living organisms on Earth. The importance of this molecule lies in its unique properties and its role in the atmosphere, especially in the stratosphere where it forms a shield against excessive UV radiation. The other choices do not play a direct role in the formation of ozone. Hydrogen does not contribute to the creation of ozone, and while nitrogen is abundant in the atmosphere, it does not react with UV light to produce ozone. Carbon dioxide also does not participate in the ozone formation process in the same way that oxygen does. Therefore, oxygen is the correct answer as it is the molecule specifically involved in the production of ozone through the energy provided by UV light.