Homework3

# Homework3 - NAME_LAUREN SLYKER STUDENT ID_S02567129...

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N AME : _ L AUREN S LYKER _________ S TUDENT ID: _ S02567129 _________ Individual Homework #3, Due Tuesday, February 16 th P ART A: I DENTIFYING THE L INES OF L IFE We have seen that when light interacts with an object some of the light is absorbed and some of the light is reflected or re-emitted by the object. By examining how different wavelengths of light are absorbed and reflected (or re-emitted) we can determine information about the composition of the atmosphere or surface of an unknown planet or moon. In the graph shown below in Figure 3 (called an absorption spectrum) , the percentage of light absorbed by water in Earth’s atmosphere (as measured between 0.7 μ m and 10 μ m) has been plotted over a range of wavelengths. Recall that a micrometer ( μ m) is equal to 10 -6 meters (m). Note: The distinction between emission and absorption, and the physical situations that lead to them, can be confusing. If you are not clear on all this, review the first part of the group activity on how the different spectra arise. Basically any hot object emits a smooth continuous spectrum, mostly visible light if it’s a star at thousands of degrees and infrared radiation if it’s a planet at hundreds of degrees. Very hot gases have emission lines superimposed by atomic transitions of the elements within the gas—a spectral fingerprint. When we do remote sensing we look at a cool object like a planet in reflected light from a star. The reflected radiation has regions removed or “eaten away” at just those wavelengths corresponding to the major atomic or molecular transitions of the surface or atmospheric material of the planets. That’s how we’ll one day figure out what distant extrasolar planets and their atmospheres are made of. Rather than showing emission, or the amount radiated by the illuminating star, the graph below shows absorption, the amount or percentage of radiation taken away by atoms or molecules. So high values of absorption means we see less radiation at those wavelengths. 1 Wavelength ( μ m) 0.1 0.2 0.5 1.0 2.0 5.0 10 50 100 Absorption (%) Water (H 2 0) Figure 3

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In the table below we have identified the approximate range of wavelengths and corresponding names (types) for the entire spectrum of electromagnetic radiation (light). T YPE OF E LECTROMAGNETIC R ADIATION (L IGHT ) W AVELENGTH (M ETERS ) Gamma ray < 10 -11 m X-ray 10 -11 m – 10 -8 m Ultraviolet 10 -8 m – 4 x 10 -7 m Visible (VIBGYOR) 4 x 10 -7 m – 7 x 10 -7 m Infrared 7 x 10 -7 m – 10 -4 m Microwaves 10 -4 m – 10 -2 m Radio 10 -2 m – > 10 2 m 1. Identify the range of wavelengths of light that were observed to make the absorption spectrum for water shown in the graph in Figure 3. What is the name (or names) of the type of light that was used to collect this data? The range of wavelengths go from
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## This note was uploaded on 05/26/2011 for the course ASTR 102 taught by Professor Jones during the Spring '11 term at Arizona.

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Homework3 - NAME_LAUREN SLYKER STUDENT ID_S02567129...

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