ASTR 1200 Midterm #1 Review

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Astrophysical & Planetary Sciences
ASTR 1200
Juri Toomsey

What is the Copernican Principle? Why is it significance for modern astronomy? -It is the principle that the sun is the center of the universe and everything does not rotate around the earth. Simply put it shows us that we are just a small piece in a larger whole. What is meant by the phrase “the universality of laws by nature” Give three examples where it applies. Same general law applys everywhere in the universe. Protons and electrons on earth are the same as sun, gravity holds together, stars, galaxies, and clusters of galaxies, and the moon orbits earth the obeys same rules for star orbiting another star. How does research astronomy differ from research laboratory sciences such as biology and chemistry? Astronomy is different because it is remote, observational, and must be content with signals. Whereas, in biology and chemistry are mainly experimental, in astronomy you cannot actually visit a star or galaxy. Compare and contrast wave-like and particle-like properties of electromagnetic radiation? Electromagnetic radiation as a wave is the propagation speed of all EM waves is the same, speed of light is the same nothing moves faster. Particle-like it packs smallest packets or quanta of light energy, the quantum nature of light is most evident when light interacts with atoms. List seven types of electromagnetic radiation in terms of increasing photon energy. Gamma, X-rays, microwaves, UV, IR, visible light, and radio waves. How is frequency of light related to its wavelength? How does the energy of a photon depend on its associated wavelength? How are the frequency and wavelength of light related to the speed of light? Frequency and wavelength are inverse, longer wavelength, lower frequency. A photon is more energetic at a shorter wavelength. All electromagnetic spectrums of light travel at the speed of light, so by knowing the oscillations of a certain type of light we can predict its wavelength. What is a Doppler shift? When astronomers observe such shifts, what do they learn about that source of light? An increase or decrease in the frequency of sound, light, or other waves as the source or observer move towards or away from each other. Astronomers can observe spectral lines to see if the spectrograph was red shifted or blue shifted, moving away, or moving towards. How does the amount of energy emitted by a black-body carry with its temperature? How does the peak wavelength of the blackbody spectrum depend on temperature? Peak emission lines and total energy vary with temparture. Planck’s radiation law is that behavior of thermal radiation as temperature is varied. What produces spectral lines? Distinguish between emission lines and absorption lines. What determines the wavelength of spectral lines? An emission or absorption line in a spectrum that arises when an electron moves between two energy levels in an atom. A jump to a higher level requires an input of energy, and produces a dark absorption line. A drop to a lower level releases energy, producing a bright emission line. Different elements have unique emission and absorption lines, like a finger print, so scientists can determine what frequency an element is emitting. Under what conditions will a cloud of hot gas produce a continuous spectr
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