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Radiation has always been a part of the environment of mankind. One of our most important radiant resources is the sun. Without the light and the warmth from the sun there would be no life on earth.
The radiation reaches us from cosmos and we ourselves contain small amount radioactive matters.
Natural sources of radiation has always effected us humans but our habits of life has change and thereby the ways we are exposed to radiation. We are for example sunning ourselves more than before and therefore have the effect of UV radiation increased.
Electromagnetic
radiation
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Visible light which are measured
in wavelengths from 380 to
770 nanometer (nm).
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Ultraviolet
radiation – UV
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Invisible light (under 380 nm)
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Infra-red
radiation – IR
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Invisible light (between 770
and 5000 nm)
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Ultraviolet radiation
The short ultraviolet beams are good in small doses. A little UV helps your body to produce vitamin D.
To much UV gives you a nice tan, that’s true but at the same time it makes the skin age in pre-time.
The invisible UV beams are divided in three groups:
1. UV-A beams (315-380 nm)
These beams are the least dangerous ones. They give the skin a light tan and makes the skin age in pre-time.
UV-A beams effect the eyes. They contribute to make the retina cloudy. Twilight vision deteriorates.
In the long run it can develop cataract.
2. UV-B beams (290-315 nm)
These beams are more dangerous and stronger than UV-A. UV-B burns deeper and is the major reason to skin cancer. UV-B is also the beam that causes snow-blindness (it burns parts of the retina) that you can be subjected to if you spend much time outside on the snow in sunny days.
3. UV-C beams (under 290 nm)
These are the strongest and most dangerous beams. UV-C absorbs by the ozone layer and seldom reaches the surface of the earth. All glasses that have 100% protection against UV-A and UV-B are also supposed to protect the eye from UV-C radiation.
Which factors have effect on UV radiation?
Different factors have effect on the UV radiation. Those factors are among others:
1. Ozone layer
The ozone layer has got a lot of attention through the last years. In the summer we are getting information from radio & TV about the thickness of the ozone layer in weather forecasts. In what appears to be two similar sunny days with bright skies, can through the thickness of the ozone layer, transmit different amount of UV radiation. Days when the ozone layer is thinner you will get tanned faster, you are in other words exposed to more UV radiation
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2. Clouds
The thickness of the clouds has importance in how much UV radiation that is transmitted. A thin cloud hardly reduces the UV radiation at all. It’s easy to think that the cloud protects you since the heat from the sun disappears no matter if the cloud is tick or thin.
3. Seasons
When the sun is low the UV radiation is low, that means: under the winter, early morning and late night in the summer you are not exposed to such high UV radiation. The higher sun-height by the equator gives more UV radiation than on higher latitudes.
4. Particles in the air
Particles or drops, aerosols, reduces the UV radiation if they occur in large amounts. It’s very rare here in Sweden but it sometimes occurs in larger cities like Los Angeles.
5. Altitude above sea level
The radiation gets much stronger the higher altitude above sea level you get. The radiation increases about 10% by 1000 meter. The reason for that is partly that the atmosphere generally is clearer the higher you get and the horizon is free.
6. Reflector
The quality sof the surface makes the radiation to reflect differently. Most of the natural surfaces reflects UV beams badly. The big exception is snow. A pure surface of snow can reflect as much as 90% of the UV radiation. Then it’s very important to protect your eyes, which is exposed to radiation from several directions. You run the risk of being snow-blind if you don’t protect your eyes.
Surface of water is a bad reflector, only about 10% of the UV radiation reflect from the downward
UV radiation. You should however have in mind that UV radiation reaches through the surface of the water and at the depth of 50 centimetres, 50% of the radiation is left.
A lot of people think that you only will have a tan if you are near water. If you are, it’s not thanks to the water, if anything, you have a free horizon and therefor are exposed to more UV radiation.
If you are at a little forest lake with a lot of trees around it, you will get a lighter tan than if you are by a sea. When the sun is high, 50% of the UV radiation come from the sun and 50% from the sky. That means that you are not free from radiation even if you are under a sunshade at the beach.
Sunglasses protects
To protect yourself against the dangerous UV beams you need sunglasses that have UV filter with 100% protection to UV-A and UV-B radiation. Unfortunately there are sunglasses on the market that don’t have UV filter even when they are marked with 100% UV protection. If you are using dark sunglasses that don’t have UV filter it will take away the reflex that makes you look with screwed-up eyes in the sun, which is natural, if you don’t wear sunglasses. You are therefore exposing you eyes to dangerous UV radiation. The result of this often shows in serious damages to the cornea.
Since there is reason to believe that even the blue short-wave beams are doing damage to the cornea, most of the high quality glasses protect against this up to 400 nm. All of HAGA EYEWEAR glasses have 100% UV-A and UV-B protection. They also protect against blue short-wave light (Up to 400 nm).
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