ASTR 100 Week 10 Notes Dr. Berrington
ASTR 100 Week 10 Notes Dr. Berrington ASTR 100
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This 5 page Class Notes was uploaded by Sarah Gardner on Sunday March 27, 2016. The Class Notes belongs to ASTR 100 at Ball State University taught by Dr. Bob Berrington in Fall 2016. Since its upload, it has received 15 views. For similar materials see Introduction to Astronomy: Solar System and Beyond in Astronomy at Ball State University.
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Date Created: 03/27/16
ASTR 100 Week 10 Notes Atomic Spectra continued Most of the universe is hydrogen o Simplest Spectrum o Lyman series when an electron jumps to level 1 found in UV and high-energy photons o Balmer series When an electron jumps to level Found in visible UV o Paschen series When an electron jumps to level 3 Found in radio How to calculate atomic Spectra o Energy of a photon equals difference of energy levels for electron o (Above equation in words) The photon’s energy is the difference of energy levels for an electron -27 -15 o H is Planck's constant h= 6.626 x 10 erg x s or 4.136 x 10 eV x s o Example: calculate the energy of a photon emitted for an electron jumping from Level 3 to level 2 (emission means going from a higher level to a lower level) Frequency and light have a 1 to 1 ratio Take above answer… This is known as hydrogen alpha in the red region of the visible spectrum Thermal blackbody Spectra o Opaque objects that absorb all light and emit none are blackbodies o Everything that is dense is a black body o Things that act this way: Stove burners Light bulbs Fire pokers o One can tell the temperature of an object by the Spectrum o Temperature determines overall emission - you can tell everything from the temperature Blackbody Spectrum o As you increase the temperature, the emission increases True for all wavelengths o Stefan-boltzmann law Flux given by Stefan – Boltzman Constant (from book) = 5.67 x 10 watts o Temperature determines wavelength of light with maximum intensity Wein’s Law If you increase the temperature, you decrease the wavelength If you decrease the temperature, you increase the wavelength Kirchhoff’s Laws of Radiation o German, 1821 - 1887 o Three laws of radiation (tells us different kinds of spectrum) o Law 1, Continuous Spectrum A solid liquid or dense gas excited to emit light will radiate at all wavelengths o Law 2, Emission Spectrum A low-density gas excited to admit light will radiate at a specific wavelength o Law 3, Absorption Spectrum If light comprising the continuous spectrum goes through cool low-density gas, it results in absorption Stars are absorption line Spectrum Stellar Spectra (absorption spectra) o Continuous Blackbody Spectrum Hot stars are blue Cold stars are red o Absorption lines Comes from atmosphere surrounding star Lines are dependent on temperature of the star Nebular Spectra o Emission Spectra Spectra in discrete colors Seen in low-density clouds of gas at high temperatures Mainly consists of hydrogen Example: Orion Nebula Lagoon nebula Doppler shift o Motion of an object causes wavelength to change o Example: sound waves Fire truck passing Person a hears a slightly higher-pitch. Person b hears a slightly lower pitch Indy 500 car is a dramatic example of the drop-in pitch after the car passes to The Observer o Motion away from observer = red shift (longer wavelength) o Motion toward the observer = blue shift (shorter wavelength) o Variation in frequency depends on how fast the object is moving Doppler shift in the Stellar Spectra o Formula Vr is radial velocity, c is speed of sound o Astronomical instruments Everything we know about the stars is from looking at the light from the Stars Optical telescopes Purpose: collect light as much as possible and bring to a focus Forms images o Correlates position and intensity o Allows astronomers to study the image Method to form image Refract light- bend to focus with lenses Reflect light -mirrors
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