Roche A. Samy
Activity: Greenhouse Effect
In order to set up this experiment, you will need a 150 watt, reflector faced, flood light lamp or Infra Red Heater lamp, a lampstand and a glass or thick plastic sheet.
Objective After this activity the students will be able to explain and describe:
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1) What a greenhouse effect is;
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2) What are the causes of greenhouse effect;
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3) What the dangers and concerns are;
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4) What should be done to remedy or control this greenhouse effect.
Experiment Attach a 150 watt, reflector faced incandescent lamp or an Infra Red Heater Bulb to a lampstand.
Place the palm of your hand about 10” to 12” above the lamp and switch on the lamp.
Then place a thick sheet of glass or plastic between the lamp and the palm of your hand. Then flash it in and out after every few seconds. You will feel the heat when there is no glass barrier but there is less or no heat when the glass or plastic barrier is held. In other words, the barrier does not emit the thermal infra red rays, acting like or simulates the carbon dioxide shield. This, exactly what happens in the Greenhouse Effect. Imagine the glass or plastic is made of carbon dioxide and water vapor.
Greenhouse Effect or Atmospheric Effect
Discussion This term is given to the trapping of heat energy radiated from the sun. The name derives from the solar warming observed in greenhouses although, in actual tact it is the direct result of trapping warmed air under plastic ceiling or thermal glass window. In solar greenhouses or solar houses where glass is used, the sunlight readily transmits through the glass but impedes thermal radiation, thereby trapping heat in the building. This phenomenon of greenhouse effect can be experienced by you when you left your car in the sun on a cool day and returned to find the car overheated. This is the reason why most architects plan passive solar heating structures and buildings with windows on the Southern side or (in the Southern hemisphere on the northern side), so that a large portion of heating needs are supplied by the sun. Windows on the East, West and North are minimized.
Most if not all substances absorb energy in the form of radiation, convert it into heat and then reradiate the energy. The amount of absorption and reradiation depends on the nature of the substance and the wavelength of radiation. In the atmosphere where we live, the short, visible wavelengths of the electromagnetic spectrum (EMS), are not very much affected but the carbon dioxide and water vapor in the air are absorbed by infra red radiation, (IR). About half of the solar radiation is absorbed by water(oceans and lakes), and land surfaces. These surfaces warm up and emit infra red radiation. The atmosphere in turn warms up and remits IR radiation. That part of the atmosphere’s remitted radiation that is directed downward towards the earth is called “counterradiation”, which is responsible for the greenhouse effect.
Since there is a continuous exchange of IR between the earth and the atmosphere, the air temperature is higher than normal. This high temperature is further increased by air pollution like burning coal, oil, gas, CO2, etc. The increase in CO2 in the air and reradiation over long periods of time upsets the “heat balance”.
Scientists and meteorologists note that on a worldwide scale the CO2 in the air has increased by about 25% in the past 100 years. There is a concern all over, that this increase in temperature due to CO2 may melt the ice caps, glaciers and ice mountains in the north (Alaska, Greenland etc.), raise the sea level and may drown Long Island, New YOrk, New Jersey and New Haven.
Evaluation:
Vocabulary:
Define or use each of the following words in a sentence so as to bring out the meaning of each word:
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1). Greenhouse Effect.
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6). Reradiation
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2). Infra Red Rays.
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7). Counterradiation.
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3). Thermal Radiation.
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8). “Heat Balance”
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4). Passive Solar Heating.
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9). CO2Balance.
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5). Electromagnetic Spectrum.
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10). Wavelength.
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Questions
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1). What do you understand by the term Greenhouse Effect?
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2). How do you think CO2 is added to the atmosphere constantly?
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3). What are the causes of this addition to the atmosphere?
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4). What do you think are the dangers involved by this process?
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5). It is known that increases in CO2 increases temperature in atmosphere, causes less rainfall thereby affecting agriculture. Has this anything to do with heat waves, drought and loss of crops and harvest (agriculture) in North Carolina, South Carolina and Georgia during this July/ August of 1986?
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6). How can you remedy this problem?
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7). Can you suggest solutions so that this kind of problem is not repeated in the future?
