The document summarizes information about the ozone layer, its formation and function, how it protects the Earth from UV radiation, and issues with its depletion. It discusses that the ozone layer is a concentration of ozone molecules in the stratosphere that absorbs harmful UV rays. It forms through interactions between oxygen and radiation, and maintains a balance through continuous breaking down and reforming. However, CFCs released into the atmosphere can destroy ozone molecules and cause depletion. This puts life on Earth at risk by increasing UV exposure.

1. Ozone layer and its depletion

2. The Ozone Layer
• The atmosphere is divided into five layers. It is thickest
near the surface and thins out with height until it
eventually merges with space.
1)The troposphere is the first layer above the surface and
contains half of the Earth's atmosphere. Weather occurs
in this layer.
2) Many jet aircrafts fly in the stratosphere because it is
very stable. Also, the ozone layer absorbs harmful rays
from the Sun.

4. • 3) Meteors or rock fragments burn up in the
mesosphere .
•4)The thermosphere is a layer with auroras.
It is also where the space shuttle orbits.
• 5) The atmosphere merges into space in
the extremely thin exosphere. This is the
upper limit of our atmosphere.

5. Ozone Layer:
• The ozone layer is a deep layer in the stratosphere,
encircling the Earth, that has large amounts of ozone in
it. The layer shields the entire Earth from much of the
harmful ultraviolet radiation that comes from the sun.
For nearly a billion years, ozone molecules in the
atmosphere have protected life on Earth from the
effects of ultraviolet rays. . The ozone layer filters out
and converts UV light into heat energy- this makes it a
higher temperature than other parts of the upper
atmosphere.

6. Ozone Formation:
• O₂ + (radiation < 240nm) 2O
• High energy UV radiation breaks the oxygen into two
oxygen atoms
• O₂ + O O₃ + heat
• The oxygen atom reacts with the oxygen to form the ozone
• The heat is absorbed by the air molecules and raises the
temperature of the stratosphere
• The ozone is mainly formed on the upper reaches of the
stratosphere

7. How the Ozone works:
• O₃ + (radiation < 310nm) O₂ + O
• Ozone molecules absorb UV radiation (240-310nm) This is,
chemically, the reverse of the formation of the ozone layer
• O₂ + O O₃ + heat
• The cycle continues as the oxygen atom immediately reacts
with O₂.
• Chemical energy released when oxygen and the oxygen
atom combine is converted into kinetic energy of molecular
motion (aka heat)

8. • Overall, penetrating UV radiation is converted into heat
without any net loss of the ozone.
• O₂ + O ↔ O₃
• The cycle keeps the ozone in balance
• The ozone is broken down and formed at the same
steady rate

9. THE SUN’S ULTRAVIOLET RAYS
• The sun emits energy over a broad spectrum of wavelengths:
• Visible light that you see
• Infrared radiation that you feel as heat
• Ultraviolet (UV) radiation that you can’t see or feel. UV radiation
has a shorter wavelength and higher energy than visible light.It
affects human health both positively and negatively. Short
exposure to UVB radiation generates vitamin D, but can also
lead to sunburn depending on an individual’s skin type.
Fortunately for life on Earth, our atmosphere’s stratospheric
ozone layer shields us from most UV radiation

10. •Damage to the ozone layer can cause the following:
•Skin cancer
•Cataracts
•Suppression of the immune system
•Premature aging of the skin
• Since the benefits of sunlight cannot be separated
from its damaging effects, it is important to
understand the risks of overexposure, and take
simple precautions to protect yourself.

11. Ozone Depletion:
• Chlorine radicals in the stratosphere mainly come
from CFCs, which can only be broken down by
the extremely energetic UV radiation found above
most of the ozone layer
• UV radiation strikes a CFC molecule, producing
a chlorine radical Cl• E.g.
• CFCl3 Cl• + • CFCl2

12. • The breakdown of ozone takes place in 2 propagation
steps
• Step 1: Cl• + O3 ClO• + O2
• Step 2: ClO• + O Cl• + O2
• The propagation steps repeat in a cycle
• Overall: O3 + O 2O2
• A single CFC molecule can destroy 100,000 ozone
molecules

13. • Another radical that destroys ozone is nitrogen oxide
(NO) from lightning or aircraft engines
• Step 1: • NO + O3 • NO2 + O2
• Step 2: • NO2 + O • NO + O2
• Overall: O3 + O 2O2

14. Global Warming
• Global warming refers to an unequivocal and continuing
rise in the average temperature of Earth's climate
system. Most of global warming is being caused by
increasing concentrations of greenhouse gases
produced by human activities. Future climate change
and associated impacts caused by global warming will
vary from region to region around the globe. Global
warming can be prevented by reducing the emission of
greenhouse gases.

15. Causes
• Burning of fossil fuels (Coal/Crude oil)
Power plants generate electricity
• – Transportation-----fuels for transports (E.g. LPG
,kerosene, fuel oi)
• – Industrial processes (E.g. manufacture of Industrial
processes of cement , Steel and aluminum
• Green house Gases

17. • Rapid Industrialization
• Population Explosion
• Depletion Of Natural Resources
• Natural Phenomena
• Modification Of Ecosystems

20. Effects of Global Warming:
• Increase in spread of disease
• Warmer waters and more hurricanes
• Increase in droughts and heat waves
• Melting of polar ice caps.
• Floods
• Storms and rise in sea level
• Death by smog
• Desertification and destruction of ecosystem
• Increase in volcanic activities
• Loss of biodiversity and animal extinction