Astro Study notes Ch 5
Astro Study notes Ch 5 Astr 1010
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This 5 page Study Guide was uploaded by Alikhan Ladhani on Sunday February 28, 2016. The Study Guide belongs to Astr 1010 at Georgia State University taught by in Spring 2016. Since its upload, it has received 55 views. For similar materials see Astronomy in Science at Georgia State University.
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Date Created: 02/28/16
Ch. 5 Light and Matter: Reading Messages form the Cosmos 02/22/2016 Light Light is a form of radiant energy Can act either like a wave or like a particle (photon) Waves A wave is a pattern of motion that can carry energy without carrying matter along with it Peak Through Properties of waves Wavelength- is the distance between two wave peaks Frequency- is the number of times per second that a wave vibrates up and down A light wave is a vibration of electric and magnetic fields Light interacts with charged particles through these electric and magnetic fields Wavelength, Frequency and Energy Structure of matter Nucleus contains protons (positive charge) and neutrons (no charge) Electrons (negative charge) orbit nucleus at positions set by electrical forces and energy Atomic Terminology Atomic Number = # of protons in nucleus Atomic Mass Number = # of protons + neutrons o Isotope: same # of protons but different # of neutrons o Ion: charged state with fewer electrons than protons (found in very hot gas) Phases of matter Solid Liquid Gas Phases of same material behave differently because of differences in chemical bonds Phase Changes with Temperature increase Melting- breaking of rigid chemical bonds changing solid into liquid Evaporation- breaking of flexible chemical bonds changing liquid into gas Dissociation- breaking of molecules into atoms Ionization- stripping of electrons changing atoms into plasma Energy level transitions Quantum theory- electrons in atoms are restricted to articular energy Only allowed changes in energy are those corresponding to a transition between energy levels Three Types of spectrum Continues spectrum o The spectrum shows a smooth continuous rainbow of light o The spectrum of a common (incandescent) light bulb spans all visible wavelengths Emission line spectrum o We see bright emission lines at specific wavelengths (color) but no other light o A thin or low density cloud of gas emits light only at specific wavelengths that depend on its composition, producing a spectrum with bright emission lines Absorption line spectrum o We see dark absorption lines where the cloud has absorbed lights of specific wavelengths (colors) o A cloud of gas between us and a light bulb can absorb light of specific wavelengths leaving dark absorption lines Chemical fingerprints Each type of atom has a unique set of energy levels Each transition corresponds to a unique photon energy Downward transitions produce emission lines Upward transitions produce absorption lines Energy Levels of Molecules Molecules have additional energy levels because they can vibrate and rotate Lots of transitions and spectral features (infrared) Properties of thermal Radiation Hotter objects emit more lights at all frequencies per unit area Hotter objects emit photons with a higher average energy measuring the shift in lights we generally measure the Doppler effect from shifts in the wavelengths of spectral lines when light is moving away then the spectrum will shift to the right when the light is towards us then shift to the left becoming more blue Doppler shift tells us only about the part of an objects motion toward or away from us Spectrum of a rotating object Doppler shifts form the sides of a rotating object spread out its spectral lines Spectral lines ae wider when a object rotates faster ▯
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