You are a biological spectroscopist in grade school and are working at Argonne N
ID: 54568 • Letter: Y
Question
You are a biological spectroscopist in grade school and are working at Argonne National Lab collecting X-ray absorption spectra. Some of your data is shown in the figure below in red. Your advisor said that he would never publish anything that looks as noisy as your data and is required you to improve your signal to noise significantly. After a lot of engineering, you come up with a new way to take multiple data sets during your beam time, which not only saves man hours (which saves money) but also improves your signal to noise so that your absorption spectra now looks like the black spectrum in the figure below. Your advisor is eminently pleased and tells you to write a paper to submit your technique to the scientific journal review of scientific instruments.
(a.) If the red spectrum represents one measurement, how many measurements did you have to collect and average to get the black spectrum?
Figure 3: X-ray absorption spectra of a molecular system. Each division on the y-axis is 1 x 10-3 arbitrary units. Lima, F.A.et al. Review of Scientific Instruments 82, p. 63111, 2011 7.10 7.127. 7.167.18 7.20 7.22 7.24 X-ray energy [keVExplanation / Answer
Ans.)
A black body radiator is a theoretical object that is totally absorbent to all thermal energy that falls on it, thus it does not reflect any light so appears black. As it absorbs energy it heats up and re-radiates the energy as electromagnetic radiation.
These must be sources of thermal energy and must be sufficiently opaque that light interacts with the material inside the source. Examples of such objects include the tungsten filaments of incandescent lamps and the cores of stars. The continuous spectrum produced by a black body is distinctive and can be shown as an intensity plot of intensity against emitted wavelength. This plot is called the blackbody curve or the Planck curve, after the German physicist Max Planck who first postulated that electromagnetic radiation was quantised.
Two key points should be apparent. Firstly, a hotter object emits more energy at every wavelength than a cooler one. Secondly, the hotter the object, the shorter the wavelength of the peak of the curve.
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