13-02-2013, 01:49 PM
EFFECT OF UV RADAIATION
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INTRODUCTION
In the present 21st century world, one does not need to say about ultra violet rays, it is the most ignited topic in this era. From the common man to the Academicians, UV rays hold an important place in their debate.
UV rays have been discussed for a long time all around the world especially after the discovery of the hole in the ozone layer in 1990s.The hole meant the approaching slow death of our mother earth. A lots of studies on this topic has been undertaken by many people and organizations such as the United Nations, Green Peace, etc.
Even when the whole world only speaks about this great calamity that has befallen on our mother earth, it would surely be a great injustice on part of the young generation as this slow killer is growing old with the young generation and they are the one who should live on this earth with this growing menace. Thus taking into consideration of these points, this project has been taken up not only to know about UV rays but also how it affects the bio diversity of our planet and how its effect can be minimized.
ULTRAVIOLET RAYS
In 1801, the German Physicist Johann Wilhelm Ritter, found that there is existence of some invisible rays beyond the violet end of the visible spectrum of the light. Those invisible rays darken silver chloride even more efficiently than visible light.
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range of 10 nm to 400 nm, and energies from 3 eV to 124 eV.
• Latitude and elevation of the location: -
At high-latitude Polar Regions, the sun is always low in the sky. So the sunlight passes through atmosphere and most of the UV-B rays are absorbed. For this reason, average UV-B exposure at the poles is over a thousand times lower than at the equator.
• Cloud Cover: -
The reduction in UV-B exposure depends on the thickness of cloud cover.
• Proximity to an industrial area: -
Due to the protection offered by photochemical smog, industrial processes produce ozone, one of the most irritating components of smog. So it absorbs UV-B. This is thought to be one of the main reasons of ozone losses in the southern hemisphere. The loss has not been mirrored in the northern hemisphere.
UV-C (100-280 nm): -
UV-C rays are highest energetic and most dangerous type of ultraviolet light. Exposure to it can even lead to death. Little attention has been given to UV-C rays in the past since they are filtered out by the atmosphere. However, their use in equipment such as pond sterilization units may pose an exposure risk, if the lamp is switched on outside of its enclosed pond sterilization unit.
EFFECTS OF UV RADIATION ON NATURE
The effects of UV radiation on earth’s ecosystems are not completely understood. Even isolating the effects of UV-A versus UV-B is somewhat arbitrary. Studies have shown that increased UV radiation can cause significant damage, particularly to small animals and plants. Phytoplankton, fish eggs, and young plants with developing leaves are particularly susceptible to damage from over exposure to UV.
Solar UV radiation levels are highest during the middle of the day. In total, almost half the daytime the total UV radiation is received during the few hours around noontime. The sunlight reaching us consists of approximately 0.5% of UV-B radiation in terms of radiant energy. Clouds, as well as ozone have a tremendous affect on UV radiation levels
DAMAGE TO MARINE LIFE
The penetration of increased amounts of UV-B light has caused great concern over the health of marine plankton that densely populates the top 2 meters of ocean water. The natural protective response of most chlorophyll containing cells to increased light-radiation is to produce more light-absorbing pigments but this protective response is not triggered by UV-B light.
Another possible response of plankton is to sink deeper into the water but this reduces the amount of visible light that they need for photosynthesis, and thereby reduces their growth and reproduction rate. In other words, the amount of food and oxygen produced by plankton could be reduced by UV exposure without killing individual organisms.
HARMFUL EFFECTS ON HUMANS
Being the one which commonly affects our health, we usually discuss the harmful effects of UV-B. The consequences of increased exposure of the human body to UV-B radiation will in the first instance be characterized by the physical properties of this type of radiation. UV-B radiation does not penetrate far into the body as most of it is absorbed in the superficial tissue layers of 0.1 mm depth.
This limits the primary effects to the skin and the eyes. However, there are also systemic effects. These start with a primary reaction in the superficial layers, but have consequences throughout the body. It is the main cause of sunburn and tanning and it has some influences on the immune system too. UV-B radiation is also the main cause of snow blindness and an important factor in the induction of cataracts. UV-B radiation contributes significantly to the ageing of the skin and eyes and it is the UV-B range that is most effective in causing skin cancer.