6.3 Atmosphere Notes - Answer KeyEnergy from the sun is known as solar energy. Earth only receives a small amount of

the sun’s energy. This small amount powers the atmosphere, oceans, and the Earth’s surface.

Energy reaches Earth by electromagnetic waves. These waves are classified by wavelength. Most energy from solar radiation (sun’s energy) reaches Earth in one of three forms: visible light, infrared light, and ultraviolet radiation.

Before the sun’s rays can reach Earth’s surface, they must pass through the atmosphere. Some energy is absorbed within the atmosphere while some is reflected.

Clouds are good “mirrors” which reflect a large amount of the incoming solar energy. About 30% (or 1/3) of all the sun’s energy is reflected back into space. Only about 20% is used by the Earth’s atmosphere. That means the remaining portion, or about 50% (1/2) of the sun’s energy goes into the surface of the Earth. Together, the clouds, the atmosphere, and the surface of the Earth are factors in Earth’s solar energy budget.

When Earth’s surface is heated, some of the energy returns to the atmosphere as infrared radiation. Not all of the heat can make it back out into space. Much of it is absorbed by gases in the air. The energy from the absorbed radiation heats the gases in the air. These gases form a “blanket” around the Earth that holds heat in the atmosphere. This causes the greenhouse effect.