What are the three factors that affect the amount of UV radiation in the natural environment?

• A. height of the sun; altitude
• B. ozone depletion; altitude
• C. height of the sun; ozone depletion
• D. height of the sun; altitude; ozone depletion

Answer: (D)

UV radiation reaching the Earth's surface depends on three influences: how high the sun is in the sky, the elevation of the location, and how much ozone is in the atmosphere. When the sun is high, its rays pass through a shorter path of air, so more UV gets through; when the sun is low, the rays travel farther and more UV is absorbed or scattered. At higher elevations, the atmosphere is thinner, giving UV less air to traverse and less absorption, so UV levels are higher. Ozone in the atmosphere absorbs a lot of UV radiation, especially UV-B; when ozone is depleted, less UV is absorbed and more reaches the surface. Because all three factors contribute to the amount of UV that arrives, the combination includes the height of the sun, altitude, and ozone depletion.