cammer8 's List: Atmosphere

• All bodies emit energy in the form of electromagnetic  radiation. Light is a form of electromagnetic radiation. So is infrared heat and  ultraviolet radiation. Different types of radiation are shown in Figure 1.1. The  type of radiation emitted by a body depends upon its temperature. Hotter objects  release more energetic radiation. The Sun, for example, emits light wave and  ultraviolet energy. The Earth, being much cooler, emits radiation in the  infrared part of the spectrum. Living things, including us, also emit radiation  in the infrared part of the spectrum. This energy is known as heat energy.
• The transfer of radiation may be accomplished by direct absorption by the cooler  object of energy emitted by the warmer one. Food placed under a grill absorbs  energy radiated from the heating elements. Similarly, the Earth absorbs energy  emitted from the Sun. How much the cooler object heats up depends upon the  nature of that object. Certain materials like rock require much less energy to  raise their temperature than others, such as water. That is to say, water has a  larger heat capacity than rock (about 5 times larger).
• Transfer of radiation can occur in other ways besides absorption. Certain  material bodies, for example glass or pure air, are transparent to visible  radiation (light), allowing the energy to pass straight through without  absorption. This is not the case for infrared radiation, which is trapped  (absorbed) by glass and certain greenhouse gases. Other material bodies neither  absorb nor allow through radiation, but reflect it back. Light surfaces such as  snow and ice are good reflectors of visible radiation.
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  1.5. Conduction

   

  Transfer of energy can also be made by conduction, if two  objects are in contact. A heating element of a kettle heats its water by  conduction of energy. Metal is a good conductor, as is water. Air is a poor  conductor of energy and therefore acts as a good insulator, as, for example,  between the outer and inner skins of a cavity wall house, or between the human  body and outside air by air spaces between fibres of clothing.

   

  1.6. Convection

   

  Convection of energy involves the movement of the body storing  the energy. Clearly, convection can only occur in fluids - liquids and gases.  Both air and water act as convecting agents for the transfer of energy. Because  air is a poor conductor of energy, convection is a major process of energy  movement in the Earth's atmosphere. In the atmosphere, convection occurs when a  shallow layer of air in contact with a hot surface warms by conduction, acquires  buoyancy (warmer air is less dense than colder air), and rises, taking with it  the energy that it stores.

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