ultraviolet (UV): light rays that compose part of the invisible portion of the electromagnetic spectrum. Excess exposure to UV radiation can be harmful to eyes and skin resulting in sunburn, skin cancer, cataracts, etc.
UVA: a component of ultraviolet radiation that can pass through window glass and penetrate the layers of the skin. This light is most intense during early morning and afternoon hours and is responsible for tanning of the skin and wrinkles. Greater than 90% of UV radiation is composed of UVA.
UVB: a component of ultraviolet radiation that is most intense during midday. Unlike UVA, it cannot penetrate window glass, but is associated with sunburn.
