MCQ Detailed View

The ozone layer is a thin, protective shield found in the stratosphere, a region of Earth's atmosphere located around 10 to 50 kilometers above the surface. Its main role is to absorb harmful ultraviolet (UV) radiation coming from the Sun, preventing most of it from reaching the Earth's surface. This protection is essential because excessive ultraviolet rays can be extremely damaging to living organisms.

When sunlight passes through the atmosphere, it contains different types of energy waves: infra-red radiation, visible light, and ultraviolet radiation. Among these, ultraviolet radiation is the most harmful because it has high energy that can damage DNA in cells, cause skin cancer, eye cataracts, and harm plants and animals. The ozone layer absorbs about 97–99% of the Sun's ultraviolet-B (UV-B) rays, allowing only safe levels of radiation to pass through to the ground.

Infra-red radiation, on the other hand, is mostly responsible for heat and is not blocked significantly by the ozone layer. X-rays and gamma rays are mostly absorbed by other atmospheric layers before reaching the surface and are not the primary focus of ozone protection. The unique chemical structure of ozone molecules (O₃) makes them highly effective at absorbing UV rays and converting their energy into harmless heat.

Human activities, such as the release of chlorofluorocarbons (CFCs), have in the past damaged the ozone layer, creating what was called the ozone hole. This thinning of ozone led to increased levels of UV radiation reaching Earth's surface, causing health and environmental concerns. International efforts, like the Montreal Protocol, have helped reduce ozone-depleting substances, allowing the ozone layer to recover gradually.

Therefore, the correct answer is Ultraviolet radiation, as the ozone layer’s main function is to prevent harmful UV rays from entering the lower atmosphere and protect life on Earth.