UVA rays have the longest wavelengths, followed by UVB, and UVC rays which have the shortest wavelengths. While UVA and UVB rays are transmitted through the atmosphere, all UVC and some UVB rays are absorbed by the Earth’s ozone layer. So, most of the UV rays you come in contact with are UVA with a small amount of UVB.
Like all forms of light on the EM spectrum, UV radiation is classified by wavelength. Wavelength describes the distance between the peaks in a series of waves.
- UVB rays have a short wavelength that reaches the outer layer of your skin (the epidermis)
- UVA rays have a longer wavelength that can penetrate the middle layer of your skin (the dermis)
Both UVA and UVB rays can cause damage to your skin. Sunburn is a sign of short-term overexposure, while premature aging and skin cancer are side effects of prolonged UV exposure.
Certain oral and topical medicines, such as antibiotics, birth control pills, and benzoyl peroxide products, as well as some cosmetics, may increase skin and eye sensitivity to UV in all skin types. Check the label and ask your doctor for more information.
Sunlight is not the only source of UV radiation you may encounter. Other sources include:
- Tanning booths
- Mercury vapor lighting (often found in stadiums and school gyms)
- Some halogen, fluorescent, and incandescent lights
- Some types of lasers