The sun emits ultraviolet rays, shortly called UV rays.
UV rays are invisible light waves that have shorter wavelengths than the visible light. Visible wavelengths cover a range from approximately 400 to 700 nm. while invisible wavelengths with stronger penetrating power are shorter than 400 nm. Based on the measurement of their wavelengths, UV radiation is classified into three primary types: ultraviolet C (UVC), ultraviolet B (UVB) and ultraviolet A (UVA). All types of UV radiation have the potential to damage eyes and skin. However each type affects eye and skin differently.
- Ultraviolet C or UVC (wavelengths: 100–280 nm.)
- UVC is the most powerful ray. It is the most damaging to the skin and eyes. Normally, the majority of UVC is absorbed by the ozone layer in the atmosphere. However, the recent ozone depletion in the atmosphere allows more harmful UVC penetration into the earth, causing health–related conditions.
- Ultraviolet B or UVB (wavelengths: 280 – 320 nm.)
- Compared to UVC, UVB has a lower energy. It is mostly absorbed by the ozone layer, but some does reach the earth’s surface. UVB affects the epidermis (outer layer of the skin) and increases the melanin production. This results in skin damages e.g. sunburn, blistering, dark spots and wrinkles as well as an increased risk of skin cancer. In relation to the eyes, UVB affects the corneas, causing eye problems, such as severe irritation and light sensitivity.
- Ultraviolet A or UVA (wavelengths: 320 – 400 nm.)
Although UVA with longer wavelengths is less powerful than UVC and UVB, UVA is the one that largely penetrates the eyes through the lens and retina. Excessive exposure to UVA has been associated with the developing of cataract. There is clinical evidence revealing that UVA is one of the potential risk factors that contribute to macular degeneration described as a blurred or no vision in the center of the visual field.
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