|
| Getting a Natural Tan | UVA and UVB rays are able to pass through the Earth’s atmospheric filter and reach the Earth. The quantity of UVA rays reached to the earth is more than UVB rays because the filter hinders shorter wavelengths of UVB being reached to the earth. UVC light is filtered and cannot reach to the earth. If it wasn’t filtered, it would lead to such negative effect as the depletion of the ozone layer in the atmosphere.
UVA and UVB light waves help the skin to get a tan, that’s why they are used in special lamps in tanning equipment.
The quantity of the outdoor ultraviolet sunlight is about 95 percent UVA and 5 percent UVB, but the percentage can be changed due to atmospheric, seasonal and geographic conditions. The earth’s ozone layer is an invisible filter that hinders the reach of different forms of harmful radiation and UVB light to the atmosphere.
The angle in which sunlight hits the ozone layer depends on the quantity of rays being blocked.
At noontime, with the sun being highest in the sky, sunlight is reaching the ozone layer at a straight “up and down” angle like arrows. Such angle makes the sunlight possible to enter the ozone layer without any difficulty.
The most intense rays cannot be prevented by ozone layer from entering the atmosphere, that’s why the most quantity of UVB light enters the atmosphere at noon. In the late afternoon the ozone layer becomes thicker and the quantity of filtered UVB rays increases due to the position of the angle. No UVB light is filtered through the ozone and reached to the atmosphere when the sun is on the horizon at dawn and dusk, that’s why only UVA light reaches the atmosphere.
The time of year can also influence the angle in which sunlight reaches the ozone layer.
In June the sun locates higher in the sky in the Northern Hemisphere comparing with December, when the position of the sun in the sky is very low in the Northern Hemisphere.
In December the quantity of UVB light that reaches the ozone layer is very small due to its low angle. In June the quantity of UVB light that reaches the ozone layer is big due to the high position of the sun in the sky. The quantity of UVA rays changes periodically all the year round due to the ability of the ozone layer to block UVA rays.
UVB rays are used to produce Vitamin D in the body due to their bigger intensiveness comparing with UVA rays. UVB light is more prone to lead to sunburn than UVA, noontime sunshine is more intense and dangerous for the skin comparing with sunshine observed at dawn or dusk.
During indoor tanning both types of rays are used to avoid indoor tanners from getting burned and help them to get a tan quickly.
Skin, the biggest organ in the human body, performs a protective function in a human body: it defends the body from negative effects of the environment, air, water and other things that contact with the skin daily. Skin regulates body temperature and its sensory receptors help people feel things. The skin is very important for human’s health.
|
|
