Ozone absorbs the most powerful ultraviolet light wavelengths, known as UV-C and UV-B, which are harmful to living beings. Other types of UV light are also absorbed by oxygen molecules. Ozone and oxygen molecules can absorb 95 to 99.9 percent of the UV energy that hits our planet. The remaining 0.1 to 5 percent reaches the surface of the earth where it can cause damage to living organisms including humans.
When solar radiation strikes the ozone layer, it produces reactive oxygen species (ROS) which can be harmful to living organisms. Therefore, animals have evolved mechanisms to protect themselves from these effects. Humans are not immune to solar radiation; indeed, we are one of the main causes of ozone depletion. However many products available on today's market help us avoid direct exposure to sunlight while still getting a dose of vitamin D. These products include sunscreen, sunblock, and tanning beds.
In conclusion, the ozone layer protects life on Earth by absorbing most of the solar radiation that would otherwise cause damage. Some solar radiation is always able to reach the ground. Our ecosystem has developed ways to protect itself from this effect.
Oxygen and nitrogen molecules absorb UV-215 and other high-energy radiation, fracture, and contribute to the formation of ozone. The only gas in our environment that absorbs the UV-215 to UV-280 wavelength range is ozone (plus everything oxygen does).
Ozone is formed when ultraviolet light breaks down oxygen molecules. The first step is usually to break one of the oxygen-oxygen bonds, leaving an oxygen atom with a free electron orbiting it. This means that now there is an area on the orbital that isn't filled with electrons, which makes it easier for another photon to knock out another electron from this site. The end result is two photons breaking two more oxygen-oxygen bonds, creating four more oxygen atoms with free electrons orbiting them. These new oxygen atoms join together to form some ozone.
The most common form of ultraviolet radiation is sunlight. The sun's energy is distributed across the spectrum, but most of it is in the lower part of the spectrum. Longwave ultraviolet radiation has wavelengths greater than 290 nm, while shortwave ultraviolet radiation has wavelengths less than 290 nm. Ozone absorbs both types of radiation. Ultraviolet radiation can also come from artificial sources such as sunlight through glass or plastic. When this radiation hits atmospheric gases such as oxygen or nitrogen, their molecules can be excited into higher energy states without breaking their chemical bonds.
UV-B energy from the sun is absorbed by ozone. When an ozone molecule absorbs UV-B, it splits into an oxygen molecule (O2) and an oxygen atom (O). The oxygen atom becomes part of another ozone molecule or reacts with other substances to form reactive oxygen species such as O3-, HO2+, and H2O+. These compounds are called photochemical oxidants because they are produced by the action of light on oxygen.
The split ozone molecule can also join together with another ozone molecule to form new ozone molecules. This process requires both molecules to have their three electrons separated from their four nuclei. If only one of the molecules has its four nuclei instead, the result is a compound known as dioxygen (O2). Otherwise the term "bond" would be inappropriate since there is no covalent bond between the two atoms after they separate.
As a result of this splitting and rejoining, most of the UV-B radiation that reaches the earth's atmosphere is prevented from reaching the surface. Only about 5% makes it through to cause damage to living organisms on land and in water. That's why periods of high atmospheric ozone concentration block out much of the sun's heat and energy at the Earth's surface.
Ozone protects life by absorbing harmful ultraviolet radiation from the sun.
All UVC and most UVB are absorbed by ozone, water vapour, oxygen, and carbon dioxide when sunlight travels through the atmosphere. Ozone is a highly powerful UV radiation absorber. Water vapour in the atmosphere blocks out much of the sun's heat, but also blocks out most of the light from the sun, including some of the most harmful ultraviolet radiation.
Oxygen and carbon dioxide also block out some of the sun's heat, but they too allow through some light, which means that both gases play a role in regulating the temperature of Earth's surface. Overall, these four substances remove more than 90% of solar energy before it reaches the surface of Earth.
The remaining 10% of solar energy reaches the surface of Earth. This occurs because light waves with shorter wavelengths (blue to red) are able to pass through earth's atmosphere. These waves contribute to global warming because they contain more energy than longer wavelength waves.
Solar activity affects how much of this light gets through to space. The amount of cosmic rays flowing into Earth's atmosphere increases when solar activity increases. These rays interact with atoms in the atmosphere, producing particles that can cascade down onto Earth's surface.
If you live in an area where sunlight exposure is a concern, use an umbrella or take a shade tree camping.