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Ozone is found in the atmosphere, particularly the middle atmosphere (stratosphere), where it absorbs ultraviolet (UV) radiation from the sun and protects Earth from being exposed to extreme UV levels. Exposure to UV radiation has been linked to skin cancer, damage of the eyes; cataract and blindness,etc. The ozone layer is the common term for the high concentration of ozone that is found in the stratosphere around 15–30km protects life on earth by absorbing harmful ultraviolet-B (UV-B) radiation from the sun.

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The ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (UVR) from the sun, protecting life on Earth from its potentially harmful effects. When the sky is clear, there is an inverse relationship between stratospheric ozone and solar UVR measured at the Earth’s surface. That is,the lower the ozone levels, the higher the solar UVR.

The level of UVR from the sun measured at the Earth’s surface varies linearly with latitude. There are higher UVR levels nearer the equator and lower UVR nearer the poles

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Ozone absorbs UV-B radiation from the sun. When an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O₂) and a separate oxygen atom (O). Later, the two components can reform the ozone molecule (O₃). By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface.

Ozone is being produced and destroyed all the time. As well as UV-B, the sun also emits another form of ultraviolet light, UV-C. When UV-C light reaches the stratosphere, it is completely absorbed by oxygen molecules and never reaches the Earth's surface. UV-C splits oxygen molecules into oxygen atoms. These single atoms then react with other oxygen molecules to produce ozone. So, these reactions increase the amount of ozone in the stratosphere.

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The ozone layer in the stratosphere absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of UV light called UVB. UVB is a kind of ultraviolet light from the sun (and sun lamps) that has several harmful effects.

Ozone absorbs UV-B radiation from the sun. When an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O₂) and a separate oxygen atom (O). Later, the two components can reform the ozone molecule (O₃). By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface.

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When UV radiation reaches ozone layer, ozone molecules present at the layer absorb its energy and decompose to form oxygen which is more stable than ozone. One ozone molecule decomposes to form one oxygen atom and a normal oxygen molecule. Hence the energy of UV radiation is absorbed in ozone layer even before reaching earth's surface. That's how ozone layer protects us from UV
radiation.

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Stratospheric ozone protects us from much of the Sun's harmful ultraviolet radiation by interacting with UV rays in a series of chemical reactions that are constantly breaking ozone apart and reforming it.Ozone is being produced and destroyed all the time. As well as UV-B, the sun also emits another form of ultraviolet light, UV-C. When UV-C light reaches the stratosphere, it is completely absorbed by oxygen molecules and never reaches the Earth's surface. UV-C splits oxygen molecules into oxygen atoms. These single atoms then react with other oxygen molecules to produce ozone. So, these reactions increase the amount of ozone in the stratosphere.Manmade chemicals containing halogens were determined to be the main cause of ozone loss. These chemicals are collectively known as ozone-depleting substances (ODSs). ODSs were used in literally thousands of products in people’s daily lives around the world.

The most important ODSs were chlorofluorocarbons (CFCs), which at one time were widely used in air conditioners, refrigerators, aerosol cans, and in inhalers used by asthma patients. When a CFC molecule reaches the stratosphere, it eventually absorbs UV radiation, causing it to decompose and release its chlorine atoms. One chlorine atom can destroy up to 100,000 ozone molecules. Too many of these chlorine and bromine reactions disrupt the delicate chemical balance that maintains the ozone layer, causing ozone to be destroyed faster than it is created.

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Ozone is extremely valuable since it absorbs a range of ultraviolet energy. When an ozone molecule absorbs even low-energy ultraviolet radiation, it splits into an ordinary oxygen molecule and a free oxygen atom. Usually this free oxygen atom quickly re-joins with an oxygen molecule to form another ozone molecule. Because of this "ozone-oxygen cycle," harmful ultraviolet radiation is continuously converted into heat.

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Ozone absorbs UV-B radiation from the sun. When an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O₂) and a separate oxygen atom (O). Later, the two components can reform the ozone molecule (O₃). By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface. The ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (UVR) from the sun, protecting life on Earth from its potentially harmful effects. When the sky is clear, there is an inverse relationship between stratospheric ozone and solar UVR measured at the Earth’s surface. That is,the lower the ozone levels, the higher the solar UVR.

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Ozone is less stable than oxygen. When UV radiation reaches ozone layer, the ozone molecules decompose to form oxygen molecules which are more stable. So even before UV radiation can reach earth's surface, its energy is used up in ozone layer for forming more stable oxygen molecules.

Now you may think that due to UV radiation ozone layer depletes quickly. But in reality, reverse reaction also takes place. A free oxygen atom combines with a normal oxygen molecule to form ozone. The free oxygen atom comes from decomposition of ozone.

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The ozone layer is a natural layer of gas in the upper atmosphere that protects humans and other living things from harmful ultraviolet (UV) radiation from the sun.

Although ozone is present in small concentrations throughout the atmosphere, most (around 90%) exists in the stratosphere, a layer 10 to 50 kilometres above the Earth’s surface. The ozone layer filters out most of the sun's harmful UV radiation and is therefore crucial to life on Earth.

Ozone is extremely valuable since it absorbs a range of ultraviolet energy. When an ozone molecule absorbs even low-energy ultraviolet radiation, it splits into an ordinary oxygen molecule and a free oxygen atom. Usually this free oxygen atom quickly re-joins with an oxygen molecule to form another ozone molecule. Because of this "ozone-oxygen cycle," harmful ultraviolet radiation is continuously converted into heat.

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UV-B light from the sun is absorbed by ozone. When UV-B absorbs an ozone molecule, it splits into an oxygen molecule (O2) and a single oxygen atom (O). The two components will later be able to rebuild the ozone molecule (O3). The ozone layer prevents hazardous amounts of UV-B from reaching Earth's surface by absorbing it in the stratosphere.
Ozone is constantly being created and destroyed. UV-C is a kind of ultraviolet radiation that the sun releases in addition to UV-B. UV-C radiation is fully absorbed by oxygen molecules in the stratosphere and never reaches the Earth's surface.

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Maryam asif Shortwave UV light (100-240nm) has enough energy to knock an electron out of an O2O2bond creating an excited molecule Oexcited2O2excited which decomposes to two free radicals of oxygen. Each of the free radicals then combines with different oxygen molecules to create a net of two ozone molecules.The crux here is that the electron is not "knocked out" of the oxygen molecule, the electron is just moved to a higher energy orbital of the same oxygen molecule. Since orbitals are quantized it takes a very specific energy to make the transition happen.Now there is a second reaction. Longwave UV light (240nm - 350nm) has enough energy to knock an electron out of an O3O3 bond creating an excited molecule Oexcited3O3excitedwhich decomposes to a free radical of oxygen and an oxygen molecule.Thus oxygen protects the ground from shortwave UV, and ozone from longwave UV. Neither alone would protects us from all UV as effectively.Now the rest of the story is that all molecules bouncing around in the air are not in the same energy state due to atom-atom vibrations. So the UV absorption occurs as a "band" rather than as a "fine line" like in the absorption spectra of an atom in free space.

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Maryam asif Shortwave UV light (100-240nm) has enough energy to knock an electron out of an O2O2bond creating an excited molecule Oexcited2O2excited which decomposes to two free radicals of oxygen. Each of the free radicals then combines with different oxygen molecules to create a net of two ozone molecules.The crux here is that the electron is not "knocked out" of the oxygen molecule, the electron is just moved to a higher energy orbital of the same oxygen molecule. Since orbitals are quantized it takes a very specific energy to make the transition happen.Now there is a second reaction. Longwave UV light (240nm - 350nm) has enough energy to knock an electron out of an O3O3 bond creating an excited molecule Oexcited3O3excitedwhich decomposes to a free radical of oxygen and an oxygen molecule.Thus oxygen protects the ground from shortwave UV, and ozone from longwave UV. Neither alone would protects us from all UV as effectively.Now the rest of the story is that all molecules bouncing around in the air are not in the same energy state due to atom-atom vibrations. So the UV absorption occurs as a "band" rather than as a "fine line" like in the absorption spectra of an atom in free space.

# data[].attributes.body
Ozone is extremely valuable since it absorbs a range of ultraviolet energy. When an ozone molecule absorbs even low-energy ultraviolet radiation, it splits into an ordinary oxygen molecule and a free oxygen atom. Usually this free oxygen atom quickly re-joins with an oxygen molecule to form another ozone molecule.

# data[].attributes.body
Ozone absorbs UV-B radiation from the sun. When an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O₂) and a separate oxygen atom (O). Later, the two components can reform the ozone molecule (O₃). By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface.
Ozone is being produced and destroyed all the time. As well as UV-B, the sun also emits another form of ultraviolet light, UV-C. When UV-C light reaches the stratosphere, it is completely absorbed by oxygen molecules and never reaches the Earth's surface. UV-C splits oxygen molecules into oxygen atoms. These single atoms then react with other oxygen molecules to produce ozone. So, these reactions increase the amount of ozone in the stratosphere.

But, ozone is not the only gas in the stratosphere. Other gases containing nitrogen and hydrogen are also in the stratosphere and participate in reaction cycles that destroy ozone converting it back into oxygen. So, these reactions decrease the amount of ozone in the stratosphere.

When undisturbed, the balance between the natural processes of ozone production and destruction maintains a consistent ozone concentration in the stratosphere. Unfortunately, we, humans do not leave this natural process undisturbed…

In the mid-1970s, scientists realised that the ozone layer was threatened by the accumulation of gases containing halogens (chlorine and bromine) in the atmosphere. Then, in the mid-1980s, scientists discovered a “hole” in the ozone layer above Antarctica – the region of Earth’s atmosphere with severe depletion.

So, what causes the thinning of the ozone layer around the globe and the “ozone hole” above Antarctica?

Manmade chemicals containing halogens were determined to be the main cause of ozone loss. These chemicals are collectively known as ozone-depleting substances (ODSs). ODSs were used in literally thousands of products in people’s daily lives around the world.

The most important ODSs were chlorofluorocarbons (CFCs), which at one time were widely used in air conditioners, refrigerators, aerosol cans, and in inhalers used by asthma patients. Other chemicals, such as hydrochlorofluorocarbons (HCFCs), halons and methyl bromide also deplete the ozone layer. Most of our computers, electronics and parts of our appliances were cleaned with ozone-depleting solvents. Car dash boards, insulation foams in our houses and office buildings, water boilers and even shoe soles were made using CFCs or HCFCs. Offices, computer facilities, military bases, airplanes and ships extensively used halons for fire protection. A lot of the fruit and vegetables we ate were fumigated by methyl bromide to kill pests.

How do these chemicals deplete ozone?

When a CFC molecule reaches the stratosphere, it eventually absorbs UV radiation, causing it to decompose and release its chlorine atoms. One chlorine atom can destroy up to 100,000 ozone molecules. Too many of these chlorine and bromine reactions disrupt the delicate chemical balance that maintains the ozone layer, causing ozone to be destroyed faster than it is created.
Ozone depletion allows more UV-B radiation to reach Earth’s surface, but UV-B also varies naturally. Levels of UV-B radiation are higher in the tropics than at temperate or polar latitudes, and higher at high altitude than at sea level. UV-B also varies predictably with season (at temperate and high latitudes UV-B reaches its maximum in mid-summer), and with time of day (peak levels occurring around mid-day). Variation in cloud also has large effects.

One way of measuring this natural variation in UV-B is through the UV-index (UVI)[WHO1]. UVI is a measure of sunburning UV radiation, and is now commonly used to show UV levels in weather forecasts. The World Health Organisation (WHO) defines any UVI greater than 11 as extreme[WHO2] but with the protection of an intact ozone layer, such high UVIs only occur at high altitude in the tropics[WHO3].

Computer models are giving us insights in to UVI in a world without the Montreal Protocol (often called the ‘World Avoided’). By the middle of this century, UVI values over 25 would have occurred at most latitudes, and UVI would have reached around 50 in the tropics, so five times the current definition of ‘extreme’ UV radiation.

Damage to human health and well-being

Even with the Montreal Protocol to protect the ozone layer, we should all try to avoid too much exposure to the sun to reduce the risk of disease such as skin cancer and cataracts that are cause by overexposure to UV-B radiation. But what if the Montreal Protocol had not been successful? How would the major diseases have been affected by unchecked ozone depletion on this world-avoided?
There are strong links between over-exposure to UV radiation and the development of the three most common forms of skin cancer (malignant melanoma, basal cell carcinoma and squamous cell carcinoma). Even now, with the successful implementation of the Montreal Protocol, skin cancers are amongst the most common forms of cancer, especially in pale-skinned populations[WHO5].

Understanding how the prevalence of skin cancers would have increased with uncontrolled ozone depletion comes from computer models of the world avoided. These models combine our understanding of how ozone-depleting substances affect the ozone layer, of how changes in ozone affect UV radiation and of how UV radiation affects the incidence of skin cancers.

For example, one global model suggests that by 2030 the successful implementation of the Montreal Protocol will be preventing about two million skin cancers every year. A longer-term model focussed on health effects in people born in the USA between 1890 and 2100. This model estimates that protecting the ozone layer will have prevented a total of approximately 443 million cases of skin cancers and 2.3 million skin cancer deaths in the USA alone. This includes 8-10 million cases of malignant melanoma. As yet there are no long-term world-avoided models for skin cancers globally. However, all the existing models lead to the same conclusion. Uncontrolled ozone depletion would have substantially increased the risk of skin cancers worldwide.

# data[].attributes.body
Ozone absorbs UV-B radiation from the sun. When an ozone molecule absorbs UV-B, it comes apart into an oxygen molecule (O2) and a separate oxygen atom (O). Later, the two components can reform the ozone molecule (O3). By absorbing UV-B in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface.

Ozone is being produced and destroyed all the time. As well as UV-B, the sun also emits another form of ultraviolet light, UV-C. When UV-C light reaches the stratosphere, it is completely absorbed by oxygen molecules and never reaches the Earth's surface. UV-C splits oxygen molecules into oxygen atoms. These single atoms then react with other oxygen molecules to produce ozone. So, these reactions increase the amount of ozone in the stratosphere.