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Different UV Rays

The sun emits electromagnetic radiation in the form of light and energy. Ninety-nine percent of this radiation reaches Earth as visible light, ultraviolet (UV) rays and infrared rays (heat). The other one percent includes radiowaves, microwaves, gamma rays and X-rays. Each type of electromagnetic radiation is classified according to its energy content. Shorter-wavelength radiation produces higher energy. For example, UV rays have shorter wavelength than visible light and are, therefore, more energetic than visible light. Infrared has the longest wavelength, ranging from 1mm to 750 nanometer. UV rays are classified by wavelength band: UVA, UVB and UVC.

  1. UVA Rays

    • UVA rays have the longest wavelength and two wave ranges: UVA1, measuring 340 to 400 nanometers (nm, or billions of a meter); and UVA2, measuring 320 to 400 nanometers. UVA rays comprise 95 percent of the radiation reaching the Earth's surface. Although UVA rays are less intense than UVB and UVC rays, they are 30 to 50 times more prevalent and are equally intense throughout the day, according to the Skin Cancer Foundation. They penetrate the skin more deeply than UVB rays and are responsible for causing photo-aging, resulting in wrinkles, premature skin aging and age spots.

    UVB Rays

    • With wavelength between 290 to 320 nanometers, UVB rays are mostly absorbed by the ozone layer, though some find their way to the Earth's surface. Their intensity varies by location, season and time of the day. The intensity is greatest between 10 a.m. and 4 p.m., and is strongest in the summer. Unprotected exposure to UVB rays can cause skin reddening and sunburn, damaging the skin's superficial epidermal layers. Prolonged exposure can lead to photo-aging and the development of skin cancers.

    UVC Rays

    • UVC rays have the shortest wavelength, from 100 to 290 nanometers, and are the most intense UV rays. Their high intensity causes them to react with the ozone layer, causing the ozone layer to break down the molecules in UVC rays, thereby rendering them ineffective. Although no UVC rays from the sun reach the surface of the Earth, UVC rays are produced in certain energy-generating procedures, such as welding and they can cause certain conditions such as cataracts and macular degeneration.

    Health Warning

    • Since UV rays are not visible to the eye, people can underestimate their damaging effects. UV ray exposure can cause health problems, including premature skin aging, skin cancer, suppression of the immune system and cataracts. The Centers for Disease Control and Prevention suggests using a sunscreen with a SPF (sun protective factor) of at least 15 or higher, wearing protective clothing, shades or hats, sunglasses and avoiding exposure to UV rays during midday hours.

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