General Knowledge - Biology - Discussion

Discussion Forum : Biology - Section 1 (Q.No. 2)
Ozone hole refers to
hole in ozone layer
decrease in the ozone layer in troposphere
decrease in thickness of ozone layer in stratosphere
increase in the thickness of ozone layer in troposphere
Answer: Option
No answer description is available. Let's discuss.
55 comments Page 1 of 6.

Maryam said:   5 months ago
The ozone layer refers to the tiny layer in the atmosphere that reached the amount of the sun's height from getting to the surface of the earth.

Promise said:   3 years ago
The decrease in thickness of the ozone layer due to global warming, CFC and pollution eases the passes of ultraviolet rays into the earth which is very Poisonous to human health.

Bks said:   4 years ago
The different layers of the atmosphere

The atmosphere can be divided into layers based on its temperature, as shown in the figure below. These layers are the troposphere, the stratosphere, the mesosphere and the thermosphere. A further region, beginning about 500 km above the Earth's surface, is called the exosphere.

The red line on the figure below shows how temperature varies with height (the temperature scale is given along the bottom of the diagram). The scale on the right shows the pressure. For example, at a height of 50 km, the pressure is only about one thousandth of the pressure at the ground.

The Troposphere

This is the lowest part of the atmosphere - the part we live in. It contains most of our weather - clouds, rain, snow. In this part of the atmosphere the temperature gets colder as the distance above the earth increases, by about 6.5°C per kilometre. The actual change of temperature with height varies from day to day, depending on the weather.

The troposphere contains about 75% of all of the air in the atmosphere, and almost all of the water vapour (which forms clouds and rain). The decrease in temperature with height is a result of the decreasing pressure. If a parcel of air moves upwards it expands (because of the lower pressure). When air expands it cools. So air higher up is cooler than air lower down.

The lowest part of the troposphere is called the boundary layer. This is where the air motion is determined by the properties of the Earth's surface. Turbulence is generated as the wind blows over the Earth's surface, and by thermals rising from the land as it is heated by the sun. This turbulence redistributes heat and moisture within the boundary layer, as well as pollutants and other constituents of the atmosphere.

The top of the troposphere is called the tropopause. This is lowest at the poles, where it is about 7 - 10 km above the Earth's surface. It is highest (about 17 - 18 km) near the equator.

The Stratosphere

This extends upwards from the tropopause to about 50 km. It contains much of the ozone in the atmosphere. The increase in temperature with height occurs because of absorption of ultraviolet (UV) radiation from the sun by this ozone. Temperatures in the stratosphere are highest over the summer pole, and lowest over the winter pole.

By absorbing dangerous UV radiation, the ozone in the stratosphere protects us from skin cancer and other health damage. However chemicals (called CFCs or freons, and halons) which were once used in refrigerators, spray cans and fire extinguishers have reduced the amount of ozone in the stratosphere, particularly at polar latitudes, leading to the so-called "Antarctic ozone hole".

Now humans have stopped making most of the harmful CFCs we expect the ozone hole will eventually recover over the 21st century, but this is a slow process.

The Mesosphere

The region above the stratosphere is called the mesosphere. Here the temperature again decreases with height, reaching a minimum of about -90°C at the "mesopause".

The Thermosphere and Ionosphere

The thermosphere lies above the mesopause, and is a region in which temperatures again increase with height. This temperature increase is caused by the absorption of energetic ultraviolet and X-Ray radiation from the sun.

The region of the atmosphere above about 80 km is also caused the "ionosphere", since the energetic solar radiation knocks electrons off molecules and atoms, turning them into "ions" with a positive charge. The temperature of the thermosphere varies between night and day and between the seasons, as do the numbers of ions and electrons which are present. The ionosphere reflects and absorbs radio waves, allowing us to receive shortwave radio broadcasts in New Zealand from other parts of the world.

The Exosphere

The region above about 500 km is called the exosphere. It contains mainly oxygen and hydrogen atoms, but there are so few of them that they rarely collide - they follow "ballistic" trajectories under the influence of gravity, and some of them escape right out into space.

The Magnetosphere

The earth behaves like a huge magnet. It traps electrons (negative charge) and protons (positive), concentrating them in two bands about 3,000 and 16,000 km above the globe - the Van Allen "radiation" belts. This outer region surrounding the earth, where charged particles spiral along the magnetic field lines, is called the magnetosphere.

Vinay said:   5 years ago
It is caused by the pollution and released harmful gases into the atmosphere like carbon monoxide, nitrogen, carbon dioxide, sulphur oxide, etc.

Khadijah said:   5 years ago
It is Mainly caused by pollution of the environment harmful gases Eg; carbon4oxide act as a blanket preventing uv rays.

Gideon said:   5 years ago
It is Due to increasing levels of global warming, greenhouse effect Eg; the use of CFCs such pollutants affect the ozone layer.

Mukesh kumar said:   6 years ago
Due to pollutants in the atmosphere, ozone layer get thin or may be damaged.

Bugli said:   6 years ago
For the first time, the ozone hole was seen in Antartica which is completely free of pollution. What is the reason behind it?

Akshika said:   6 years ago
Due to pollutants in atmosphere ozone layer get thin or may be damage.

Shaz said:   6 years ago
Ozone layer is the layer that blocks the altra violet rays.

Post your comments here:

Your comments will be displayed after verification.