Wednesday, July 13, 2011

What is UV400, UVA, UVB and UVC?

Ray Ban Original Wayfarer Sunglasses Tortoise w G15 XLT Lens
Ultraviolet radiation (UV) comes naturally from the sun. There are also some manmade lamps and tools (welding tools, for instance) that can produce UV radiation. For most of us, however, the sun is the primary source of UV. UV is divided into at least three different categories based on wavelength:

Does the amount of UV protection in sunglasses matter?

  • UVA wavelengths(320-400 nm) are only slightly affected by ozone levels. Most UVA radiation is able to reach the earth's surface and can contribute to tanning, skin aging, eye damage, and immune suppresion. UV 400 Protection lenses are engineered to block 100% of all harmful blue light up to 400 nanometers

  • UVB wavelengths(280-320 nm) are strongly affected by ozone levels. Decreases in stratospheric ozone mean that more UVB radiation can reach the earth's surface, causing sunburns, snow blindness, immune suppression, and a variety of skin problems including skin cancer and premature aging.

  • UVC wavelengths (100-280 nm) are very strongly affected by ozone levels, so that the levels of UVC radiation reaching the earth's surface are relatively small.

The effects of UV radiation on earth's ecosystems are not completely understood. Even isolating the effects of UVA versus UVB is somewhat arbitrary. All UV radiation can be damaging. This knowledge has prompted many manufacturers of sun screen and sunglasses to offer products that protect against both UVA and UVB wavelengths.

While humans can choose various courses of protection, for instance avoiding noon-time sun, plants and animals are not so fortunate. 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 suspectible to damage from overexposure to UV.


1 comment:

    ic! belin แว่น


Please write your comments here...