Atmospheric Structure and Ozone

This statement is correct. The depletion of ozone concentration in the stratosphere is called the ozone hole.

The exosphere is the outermost layer of Earth's atmosphere, extending from about 500 km altitude to the edge of space. It is followed inward by the thermosphere, mesosphere, stratosphere, and troposphere (lowest).

The ionosphere, located between 60-1000 km altitude, contains ionized particles that reflect radio waves back to Earth, enabling long-distance radio communication. The exosphere (A) is too thin, stratosphere (C) contains ozone but doesn't reflect radio waves well, and troposphere (D) is where weather occurs but doesn't reflect radio waves.

The ozone layer, located in the stratosphere, primarily absorbs ultraviolet (UV) radiation from the sun. This absorption is crucial for protecting life on Earth from harmful UV rays that can cause skin cancer and damage ecosystems. IR and visible light mostly pass through the atmosphere.

Ozone is indeed a poisonous gas - at ground level it is harmful to breathe and can damage lung tissue and plant life. It is triatomic (O3, not mono-atomic), found primarily in the upper atmosphere (stratosphere, not lower), and absorbs UV radiation rather than reflecting it. Statement B is the only true statement among the options.

 Oxygen constitutes 21% of the atmosphere.

The ozone layer in the stratosphere absorbs harmful ultraviolet (UV) radiation from the sun, preventing it from reaching Earth's surface. This UV protection is crucial for living organisms as excessive UV radiation can cause skin cancer and damage ecosystems. The ozone layer does not protect against air pollution, solar heat, or sudden climatic changes.

Chlorofluorocarbons (CFCs) are synthetic compounds that break down in the stratosphere and release chlorine atoms, which catalytically destroy ozone molecules. This depletion of the ozone layer allows more harmful UV radiation to reach Earth. Oxides, sulphides, and hydroxides are not responsible for ozone depletion.

The greenhouse effect maintains Earth's warm temperature by trapping heat in the atmosphere through greenhouse gases. Without this natural effect, Earth's average temperature would be about -18°C instead of the current +15°C. It does not primarily maintain water balance, the carbon cycle, or the ozone layer.

The ozone hole is primarily located over Antarctica due to extreme cold temperatures and polar vortex dynamics that create ideal conditions for ozone depletion. The Antarctic region experiences the most severe ozone thinning, especially during spring (September-October).

CFCs (chlorofluorocarbons) react chemically with ozone molecules in the stratosphere, breaking them down. This reaction occurs when UV radiation splits CFC molecules, releasing chlorine atoms that catalytically destroy ozone.

The ozone layer absorbs harmful UV-B radiation from the sun. When ozone is depleted, more UV rays reach Earth's surface, increasing risks of skin cancer, cataracts, and ecosystem damage. Temperature effects are secondary and indirect.

Chlorofluorocarbons (CFCs) are synthetic compounds that break down in the stratosphere and release chlorine atoms, which catalytically destroy ozone molecules. This was the primary cause of the ozone hole discovery in the 1980s.

The ozone layer in the stratosphere absorbs most of the sun's harmful ultraviolet (UV) radiation, preventing it from reaching Earth's surface. This protection is crucial for preventing skin cancer and protecting ecosystems.

Air is present in the troposphere layer of atmosphere.