Tuesday April 10, 2012. (Atmospheric Heating). The Launch Pad Tuesday, 4/10/12. List and define the three mechanisms of heat transfer?. conduction. convection. radiation. Announcements. I will be available after school today until 4:45 . Latest News.
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List and define the three mechanisms of heat transfer?
U.S. Records Warmest March; More Than 15,000 Warm Temperature Records Broken
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Heat is the flow of thermal energy, and is always transferred from warmer to cooler objects.
There are three mechanisms of heat transfer:
Conduction through molecular activity.
Convection is mass movement within a substance, usually vertical motions.
Radiation(electromagnetic radiation) travels at a velocity of 186,000 miles per second in a vacuum.
radio waves, microwaves, waves, infrared, visible, ultraviolet (UV),x-rays, gamma (very short waves)
Radiation(electromagnetic radiation) consists of different wavelengths of energy:
Visible light consists of an array of colors we commonly call the “colors of the rainbow.” Rainbows are relatively common optical phenomena produced by the bending of light by drops of water.
Electromagnetic radiation is governed by basic laws.
All objects, at whatever temperature, emit radiation.
Hotter objects radiate more total energy per unit area than do cooler objects.
The hotter the radiating body, the shorter the wavelength of maximum radiation.
Hotter objects emit most of their radiation at shorter wavelengths; hence they will appear to be bluer .
Cooler objects emit most of their radiation at longer wavelengths; hence they will appear to be redder.
Objects that are good absorbers of radiation are good emitters as well.
The Earth’s atmosphere is largely transparent to incoming solar radiation.
Atmospheric effects include:
reflection (a surface’s albedo is the percent of solar radiation reflected.)
Most visible radiation reaches the Earth’s surface, and about 50% is absorbed at the surface.