Atmospheric Structure and Ozone

The atmospheric layers from Earth's surface upward are: Troposphere (0-12km, where weather occurs), Stratosphere (12-50km, contains ozone layer), Ionosphere (part of upper atmosphere, 60km+ where ions are present), and Exosphere (outermost layer, fading into space). Option C presents this correct vertical sequence.

The ozone layer in the stratosphere absorbs most of the Sun's ultraviolet (UV) radiation, protecting living organisms from harmful UV rays that can cause skin damage. It does not primarily block cosmic rays, ultrasonic waves, or infrared rays.

The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun, protecting living organisms on Earth. It does not protect against meteorites or infrared light. UV radiation can cause skin cancer and damage ecosystems.

The ozone hole is visible during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container.

Troposphere: The layer of the atmosphere closest to the earth is the troposphere. It begins at the surface of the earth and extends to about 4-12 miles. The temperature of the troposphere decreases with height. This layer is known as the lower atmosphere. Stratosphere: Above the troposphere is the stratosphere, which extends to about 30-35 miles above the earth's surface. Temperature rises within the stratosphere, but still remains well below freezing. Mesosphere: From about 35 to 50 miles above the surface of the earth, lies the mesosphere, where the air is especially thin and molecules are great distances apart. Temperatures in the mesosphere reach a low of -184°F (-120°C). The stratosphere and the mesosphere are the middle atmosphere. Thermosphere: The thermosphere rises several hundred miles above the earth's surface, from 50 miles up to about 400 miles. Temperature increases with height and can rise to as high as 3,600°F (2000°C). Nonetheless, the air would be cold because the hot molecules are so far apart. This layer is known as the upper atmosphere. Exosphere: Extending from the top of the thermosphere to 6200 miles (10,000 km) above the earth is the exosphere. This layer has very few atmospheric molecules, which can escape into space.

1. The amount of atmospheric ozone is measured by ‘Dobson Spectrometer’ and is expressed in Dobson unit.
   1. Chlorofluorocarbons are most likely to be present in photochemical smog. Photochemical smog is a form of pollution that is caused by the reaction of sunlight with other pollutants such as hydrocarbons and nitrogen oxides. Photochemical smog can be seen sitting over the skylines of large cities and near factories.

This is the correct answer, as statements a and b are the correct statements.

Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.

This statement is incorrect. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface.

The troposphere is the lowermost layer of the atmosphere.

The column of atmosphere is divided into five different layers depending upon the temperature condition.

The ionosphere or thermosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer.

The stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.

This is the correct answer. The main elements of atmosphere, which are subject to change and also influence human life on earth, are temperature, pressure, winds, humidity, clouds and precipitation.

All of the above factors are responsible for ozone destruction.