ASTRO 150 Study Guide - Midterm Guide: Electromagnetic Spectrum, Nuclear Force, Electromagnetism

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Abbreviated Review for Exam 1
Scales of the Universe
o Size of solar system
o Definition of the light year
o The nearest: star, galaxy
o The composition and age of the Universe
Gravity: Newton's Laws
o Gravity as a fundamental force: Central, Universal, and Cosmic
o Other Cosmic forces: Electromagnetic force, Weak Nuclear force, strong nuclear
force
Light: a form of energy=electromagnetic radiation
o wave nature: wavelength (l) x frequency (f) = speed (c for light)
o different wavelength = different 'color'
o particle nature: photon as a bundle of light energy; energy proportional to
frequency
o Brightness proportional to luminosity divided by distance squared
Electromagnetic spectrum
o short wavelength (gamma ray) to long wavelength (radio)
o high energy (gamma ray) to low energy (radio)
Thermal (blackbody) radiation - radiation from objects because they are hot
o Wien's law: wavelength of maximum emission increases with decreasing
temperature
o Stefan-Boltzmann Law: energy emitted proportional to T4
o stars are like blackbodies; hot stars are blue, cool stars are red
Spectral Lines
o Kirchoff's laws: emission, absorption, and continuous spectra
o discrete atomic energy levels correspond to discrete electron orbits
o transitions up in energy absorb photons; transitions down emit photons
o bigger energy difference between levels, higher energy photon involved
o each element has its own signature spectral lines; atomic fingerprints
Spectroscopy as the "Rosetta Stone" in astronomy
Telescopes:
o light gathering power depends on size2
o resolution depend on size / wavelength
o mechanical and optical specifications
o instrumentation: photometry, spectroscopy, imaging
o advantages and disadvantages of astronomy from space
o adaptive optics
The Sun
o surface features: sunspots, prominences, corona, etc.
o energy transport by radiation, conduction and convection
o energy production by nuclear fusion: E=mc2; 4 hydrogen -> 1 helium + energy
o solar neutrino problem
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