FIGURE ABOVE: Normalized blackbody curves for 5780 K and 255 K. (b) Atmospheric
ID: 121543 • Letter: F
Question
FIGURE ABOVE: Normalized blackbody curves for 5780 K and 255 K. (b) Atmospheric absorption in clear air for solar radiation with a zenith angle of 50 degrees and for diffuse terrestrial radiation for the portion of the atmosphere lying above the 11-km level near the middle-latitude tropopause. (c) Same as (b) but for the entire atmosphere.
A) i. What gas absorbs most of the sun’s ultraviolet radiation? ii. What part of the atmosphere is this radiation absorbed in? iii. Why is it important that this radiation be absorbed?
B)What is the wavelength span for the visible window at ground level?
C)What is the wavelength span for the infrared window at ground level?
D)Why is the CO2 absorption band at a wavelength of about 15 microns more important than the CO2 absorption band at about 4.3 microns for ‘greenhouse’ warming?
Explanation / Answer
A. i Most of the sun's UV rays are absorbed by Ozone gas.
ii UV radiation is absorbed in Stratosphere.
iii. This UV radiation has very high energy. Therefore it can cause a lot of harm to flora and fauna on earth, like skin cancer, eye problems etc. So that is why it is important that this radiation be absorbed.
B. A radiation window is that radiation wavelenght which can easily pass through the atmosphere i.e. atmosphere cannot absorb radiation from these wavelenght ranges.
According to the fig., the wavelength span for the visible window at ground level is 0.4 micron to 0.7 micron. Beacuse in this range, the absorption is minimum.
C. According to the fig., the wavelength span for the infrared window at ground level is 3 to 4 micron and 8 to 14 micron. Beacuse in this range, the absorption is minimum.
D. Carbon dioxide has three absorption bands at wavelengths of 4.3, 7.5, and 15 microns.The Earth radiates long wave radiation between 15 and 20 microns. Therefore CO2 absorbs IR radiation only in 15 micron range that causes global warming.
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