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The molecules of carbon dioxide in the Earth‘s
atmosphere affect the heat balance of the Earth by
acting as a one-way screen. Although these molecules
allow radiation at visible wavelengths, where most of
5 the energy of sunlight is concentrated, to pass
through, they absorb some of the longer-wavelength,
infrared emissions radiated from the Earth‘s surface,
radiation that would otherwise be transmitted back
into space. For the Earth to maintain a constant aver age
10 temperature, such emissions from the planet must
balance incoming solar radiation. If there were no
car-bon dioxide in the atmosphere, heat would escape
from the Earth much more easily. The surface temperature
would be so much lower that the oceans might be a solid mass
15 of ice. (120 words)
3. According to the passage, the greatest part of
the solar energy that reaches the Earth is
(A) concentrated in the infrared spectrum
(B) concentrated at visible wavelengths
(C) absorbed by carbon dioxide molecules
(D) absorbed by atmospheric water vapor
(E) reflected back to space by snow and ice
For the following question, consider each of the choices separately and select all that apply
4. According to the passage, atmospheric carbon
dioxide performs which of the following functions
□A absorbing radiation at visible wavelengths
□B absorbing outgoing radiation from the Earth
□C helping to retain heat near the Earth‘s surface |
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发表于 2011-9-30 10:32:48
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