11/18/2010. Only part of the spectrum we can see. A rainbow of colors, each corresponding to a different wavelength.

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1 The sun is the source of energy to heat the Earth s surface. Solar energy makes it s way to Earth by an energy transfer mechanism called radiation. Energy transferred this way travels outwards in all directions from it s source. The sun emits an array of electromagnetic radiation of varying wavelengths. Light Heat Ultraviolet Radiation All wavelengths travel through space at the speed of light. Waves or rays come in varying length. The shortest waves are gamma rays. The longest are radio waves. Infrared radiation is felt as heat. Ultraviolet rays cause sunburn. Only part of the spectrum we can see. A rainbow of colors, each corresponding to a different wavelength. 5 1

2 Longest wavelength produces the color red. All objects, regardless of temperature, emit radiation. Shortest wavelength produces the color violet. The hotter the radiating body, the shorter the wavelengths of emission. The sun emits energy in the visible range. The Earth radiates energy in the infrared range. Objects that are good absorbers of radiation are also good emitters. Earth and Sun absorb and radiate with nearly 100% efficiency. Gases are selective absorbers and radiators. INTERACTIV E Scattering is the process by which gases and tiny particles in the atmosphere redirect light. This is how light reaches into a shaded area or room when sunlight is absent. The percentage of total radiation reflected by a surface. Albedo varies with conditions, but the averages are: 30% reflected back to space 5% by the atmosphere 20% by clouds 5% by the land/sea surface 2

3 The angle of the sun s rays influence the percentage of light reflected. The greater the angle of the sun, the longer the path through the atmosphere. Rays striking the Earth near the poles must travel through more atmosphere than those near the equator. A longer path through the atmosphere increases the amount of scattering and reflection. When albedo increases, there is less solar energy available. When albedo decreases, there is more solar energy available. The term Greenhouse Effect describes how the Earth is heated. Video Clip 3

4 Carbon dioxide (CO2) and water vapor (H2O) are the primary heat-absorbing gases. They reradiate this energy away in all directions. Some of this energy is trapped by the atmosphere in the form of heat. The Earth is about 30 degrees Celcius (50 degrees Farenheit) warmer than it would be without the an atmosphere. Since gases are selective absorbers, the atmosphere transfers most incoming heat to the Earth s surface, where it is absorbed. Air is heated when water vapor and carbon dioxide absorb the longer wavelength radiation emitted by the Earth. Any change in the air s carbon dioxide content could alter the temperature in the lower atmosphere. Fossil fuel combustion has contributed to an increase of about % of CO 2 since Significant temperature increases could lead to the melting of the polar ice caps and changes to weather patterns. 4

5 2. Sun: 2. Stove: 3. Sunscreen: 4. Electromagnetic spectrum: 5. Visible spectrum: 6. Prism: 7. Iceberg: 8. Wavelengths: Scattering: Albedo: Earth s Energy Budget: BW: Color: Solar Radiation: Greenhouse: Greenhouse Effect: Ice Age: Climate Change: 5