Atmospheric Structure and Ozone

The ionosphere is defined as the layer of the Earth's atmosphere that is ionized by solar and cosmic radiation. It lies 75 to 1000 km above the Earth. It is distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is also called as thermosphere.

The troposphere is the lowest layer of Earth's atmosphere and site of all weather on Earth. The troposphere is bonded on the top by a layer of air called as the tropopause, which separates the troposphere from the stratosphere, and on bottom by the surface of the Earth. It contains approximately 75% of the atmosphere's mass and 99% of its water vapour and aerosols. The average depth of the troposphere is approximately 17 km in the middle latitudes.

Atmospheric layers include the troposphere (0 to 16 km), stratosphere (16 to 50 km), mesosphere (50 to 80km) and thermosphere (80 to 640km). In the troposphere and mesosphere, temperature generally falls with increasing altitude, while in the stratosphere and thermosphere, temperature rises with increasing altitude. In addition to temperature, other criteria can be used to define different layers in the atmosphere. 

Exosphere is the outer fringe of Earth's atmosphere, which extends some 20000 miles from the planet. It's dominant element is hydrogen and its temperature ranges from $200^0 F$ to $1000^0 F$. The lower part of exosphere contains abundance of helium besides hydrogen and is called as “helium zone”. Hence, option D is correct.

Global warming is the overheating of the earth due to the increased concentration of greenhouse gasses. Greenhouse gasses generally traps the radiations of the earth which leads to increase in the temperature of the earth and global warming. The greenhouse gasses includes water vapor, carbon dioxide, methane, nitrous oxide, and ozone. 

The concentration of oxides increases due to the high rate of emission from the vehicle and other human activities like deforestation. The oxides form a layer which traps solar radiation to escape the earth atmosphere which leads to global warming.

The burning of fuels in the atmosphere leads to the formation of poisonous oxides and dioxides which push up the temperature of the earth and contributes to global warming. Clouds and gases reflect about one-fourth of the incoming solar radiation, and absorb some of it but almost half of incoming solar radiation falls on earth's surface heating it, while a small proportion is reflected back. Earth's surface re-emits heat in the form of infrared radiation but part of this does not escape into space as atmospheric gases (e.g., carbon dioxide, methane, etc.) absorb a major fraction of it. The molecules of these gases radiate heat energy, and a major part of which again comes to earth's surface, thus heating it up once again.The above-mentioned gases (carbon dioxide and methane) are commonly known as greenhouse gases because they are responsible for the greenhouse effect. 

The higher concentration of carbon dioxide in the atmosphere is likely to increase the temperature as carbon dioxide permits the short wavelength visible radiations to pass through it but traps the longer wavelength infrared radiation reflected by earth's surface. This is called the greenhouse effect and it results in the overall increase in the global temperature, called global warming. Carbon dioxide contributes to the 81% of the greenhouse gases because it tends to persist in the atmosphere.

The greenhouse effect can be defined as the trapping of radiations of the sun by the tropospheric gases and preventing these radiations from reflecting back to space. The tropospheric gases involved are atmospheric dust, Ozone, Carbon dioxide and water vapour. These gases are responsible for causing global warming.

The greenhouse effect can be defined as the capture and re-radiation of the infre-red radiations by the tropospheric gases like ozone, carbon dioxide, water vapours and dust. This lead to the increase in the temperature of the atmosphere, and as a result the over all temperature of the earth increases, causing global warming.

A. Ozone layer effect is the absorption of UV rays.

B. Radioactive effect is the release of the radiations by radioactive substances.

C. The greenhouse effect can be defined as the capture and re-radiation of the infre-red radiations by the tropospheric gases like ozone, carbon dioxide, water vapours and dust.

D. Solar effect is the massive release of solar flares.

Hence, the correct answer is 'Greenhouse effect'.

The process where atmospheric gases trap heat radiation from the Earth's surface, preventing it from escaping into space, is known as the greenhouse effect.

Chlorofluorocarbons (CFCs) are chemical compounds that, when released into the atmosphere, break down and release chlorine atoms that destroy ozone molecules.

The troposphere is the lowest region of the atmosphere, i;e., closest to earth's surface. It extends roughly to a height of about 11 km. This is the region of all living organisms including, animals and plants. 

Fifty percent of the total mass of the atmosphere is located in the lower $5-6$ $km$ of the troposphere. Nearly all atmospheric water vapour or moisture is found in the troposphere. So, it is the layer where most of the earth's weather takes place.