Ultraviolet rays

Ultraviolet Rays
Radiation from the sun that can be useful or potentially harmful. UV rays from one part of the spectrum (UV-A) enhance plant life. UV rays from other parts of the spectrum (UV-B) can cause skin cancer or other tissue damage.

The “ozone hole' refers to a decrease in the layer of ozone gas found high in the Earth's atmosphere, which helps to shield the planet from the sun's harmful ultraviolet rays.

Ultraviolet Rays
Uncertainty Factor
Unconfined Aquifer
Underground Injection Control (UIC)
Underground Injection Wells
Underground Sources of Drinking Water
Underground Storage Tank (UST)
Unreasonable Risk
Unsaturated Zone ...

Ionising radiation includes ultraviolet rays, radon gas and X-rays. Too much exposure to ionising radiation can be harmful, leading to increased risk of cancer. Non-ionising radiation includes visible light, radio waves and microwaves.

Smog. Hazy, polluted air caused by the combination of ultraviolet rays from the sun and automobile and industrial emissions in the atmosphere ...

The protective layer in the atmosphere, about 15 miles above the ground, that absorbs some of the sun's ultraviolet rays, thereby reducing the amount of potentially harmful radiation that reaches the earth's surface.

Ozone Layer: A layer of ozone in the lower portion of the stratosphere -- 12 to 15 miles above the Earth's surface -- which helps to filter out harmful ultraviolet rays from the sun.

See also: Water, Environment, Radiation, Atmosphere, Ozone