2.1 Energy in the Atmosphere

Guide for Reading In what form does energy from the sun travel to Earth? What happens to energy from the sun when it reaches Earth? Which color of visible light has the longest wavelength? Why would particles from volcanic eruptions make sunsets and sunrises more red?

Energy from the Sun Energy travels to Earth as electromagnetic waves Form of energy that can travel through space Classified according to wavelength The direct transfer of energy by electromagnetic waves is called radiation

Energy from the Sun Most of the energy from the sun reaches Earth in the form of visible light and infrared radiation, and a small amount of ultraviolet light.

Energy from the Sun Infrared radiation is a form of energy with wavelengths that are longer than red light. Not visible Can be felt as heat Example: lamps used to keep food warm in restaurants give off both visible red light and invisible infrared light

Energy from the Sun The sun also gives off ultraviolet radiation, which has wavelengths that are shorter than violet light. Cause sunburns Can cause skin cancer and eye damage

Energy in the Atmosphere When the rays of the sun pass through the atmosphere, some of the energy from the sun is absorbed within the atmosphere Some infrared radiation is absorbed by water vapor and carbon dioxide The ozone layer in the atmosphere absorbs most of the ultraviolet radiation Clouds, dust and other gases also absorb energy from the sun

Energy in the Atmosphere Some sun rays are reflect Clouds act like mirrors, reflecting some solar energy back into space Dust particles and molecules of gases in the atmosphere reflect light from the sun in all directions

Energy in the Atmosphere Reflecting of light in all directions is called scattering When you look in the sky, the light you see has been scattered by gas molecules in the atmosphere Gas molecules scatter short wavelengths of visible light more than longer wavelengths Why the sky is blue!

Energy in the Atmosphere When the sun is rising and setting Light form the sun passes through a thicker part of the atmosphere More light from the blue end of the spectrum is removed by scattering The remaining light from the sun contains mostly red and orange light

Energy at Earth’s Surface Some of the sun’s energy reaches Earth’s surface and is reflected back into the atmosphere Some is absorbed by the land and water and changed into heat

Energy at Earth’s Surface When Earth’s surface is heated, it radiates some of the energy back into the atmosphere as infrared radiation. The IR cannot travel all the way through the atmosphere back to space Absorbed by water vapor, carbon dioxide, methane, and other gases

Energy at Earth’s Surface Absorbed radiation heats the gases in the air and a “blanket” around earth is formed Holds heat in the atmosphere The process by which gases hole heat in the air is called the greenhouse effect. Keeps Earth’s temperature comfortable for most living things