Sun and Ultraviolet Rays
Ultraviolet radiation (UV) comes naturally from the sun. There are also some man-made 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.
Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the total light output of the Sun and is thus present in sunlight. It is also produced by electric arcs and specialized lights, such as mercury-vapour lamps, tanning lamps, and black lights. Although it is not considered ionizing radiation because its photons lack the energy to ionize atoms, long-wavelength ultraviolet radiation can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.
UV is divided into at least three different categories based on wavelength:
Types of UV Rays
- 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 ageing, eye damage, and immune suppression. 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 ageing.
- 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
The effects of UV radiation on the 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 sunscreen 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 susceptible to damage from overexposure to UV.
Solar UV radiation levels are highest during the middle of the day. In total, almost half the daytime total UV radiation is received during the few hours around noontime. Clouds, as well as ozone, have a tremendous effect on UV radiation levels. However, cloudy skies generally do not offer significant protection from UV. Thin or scattered clouds can have minor impacts on UV and even, for a short time, increase UV above what it would be on a blue sky day by further scattering the radiation and increasing the levels that reach the surface.
How Does The Sun Damage Your Eyes
Sunlight effects on the human eye
- Temporary Problems with Over-exposure to Sunlight
- Excessive watering and blinking
- Burning sensation
- Eyelid swelling
- Photophobia (difficult to look at bright light)
Eye Diseases Associated with Longtime Sun Exposure
Overexposing to UV rays may have a risk to develop following ocular disorders:
- Age-related macular degeneration
- Lid Skin cancer
How to protect your eyes from UV rays effects?
- Wear protective sunglasses. (Find sunglasses that offer both UVB and UVA protection that block at least 99% of UV rays. Make sure to get large lenses that cover the eye area for maximum protection.)
- Wear a hat while out in the sun
- Avoid going out in the sun during the middle of the day (Studies have shown that the main danger period is between 10 AM and 4 PM daily)
Read also: What is Antireflect Coating Lens