Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Environmental Issues

Question:

Read the given passage and answer the following questions:

'Bad’ ozone, formed in the lower atmosphere (troposphere) that harms plants and animals. There is ‘good’ ozone also; this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun. UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules. The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU). Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere. There should be a balance between production and degradation of ozone in the stratosphere. Of late, the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs). CFCs find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays act on them releasing Cl atoms. Cl degrades ozone releasing molecular oxygen, with these atoms acting merely as catalysts; Cl atoms are not consumed in the reaction. Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing effects on Ozone evels. Although ozone depletion is occurring widely in the stratosphere, the depletion is particularly marked over the Antarctic region. This has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole.UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth’s atmosphere, given that the ozone layer is intact. But, UV-B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers. In human eye, cornea absorbs UV-B radiation, and a high dose of UV-B causes inflammation of cornea, called snow-blindness, cataract, etc. Such exposure may permanently damage the cornea.

What is the main function of the 'good' ozone in the stratosphere?

Options:

To absorb UV radiation from the sun

To protect against greenhouse gases

To cool the Earth's surface

To increase oxygen levels

Correct Answer:

To absorb UV radiation from the sun

Explanation:

The correct answer is Option (1) –To absorb UV radiation from the sun

The 'good' ozone in the stratosphere forms the ozone layer, which plays a crucial role in protecting life on Earth. This layer absorbs the majority of the sun's harmful ultraviolet (UV) radiation. Without this protective layer, these high-energy UV rays would reach the Earth's surface in much higher quantities, causing significant harm to living organisms. UV-B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers.