1. 2.1 Energy in the Atmosphere

2. 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?

3. 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

4. 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.

6. 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

7. 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

8. 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

9. 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

10. 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!

11. 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

12. 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

13. 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

14. 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