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Published byMyah Peffer Modified over 9 years ago
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Unlocking Light The key to understanding the Cosmos
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Uses of Light Astronomers use light as a tool to “dissect” celestial objects Only direct information we can get! Collect light with various instruments Study light to determine sources
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Light Sources Atoms or parts of the atom are the source of all light Behavior of particles in Atom generates light What are these particles?
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Parts of the Atom Proton Neutron Electron
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Parts of the Atom Atoms are building blocks of matter Nucleus Protons – Positive Charge Neutrons – Neutral Orbits Electrons – Negative Charge
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Building Blocks Elements-pure substances Atoms- smallest part of an element Compound- chemically joined elements Molecule- smallest part of a compound
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Elements Periodic Table ID’s are Atomic Number (Z) Z=number of protons Atomic Mass (A) Number of Protons + Number of Neutrons
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Elements Neutral Atoms have same # of electrons and protons Ions have lost or gained some electrons Isotopes have lost or gained some neutrons
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Get Excited Electrons naturally orbit in lowest energy state Ground State If atom absorbs some energy the electron can move to a larger orbit Excited Electron
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Excited Atoms Atoms gain energy Excited (but not ionized) atoms Electrons move away from nucleus but are still orbiting
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Excited Atom Proton Neutron Electron
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Excited Atoms Electron absorbs energy to “jump up” Electron releases energy to “fall down” This Energy is Light!
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Spectra Light is released This is the Spectra of the atom Unique Distinct Fingerprint for Elements and Compounds
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Continuous Spectra Rainbow No Gaps in Colors “White” light contains all colors ROYGBIV
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Emission Spectra Dark Background Few Bright Colored Lines Spectral Lines Unique for Each Element
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Absorption Spectra Similar to Continuous Spectra Dark gaps where colors are missing Also Spectral Lines Unique for Each Element
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Kirchhoff’s Rules Describes conditions needed to form the 3 types of spectra Can be related to Astrophysical conditions We can infer information from type of spectra
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Rule #1 Hot, opaque light source Continuous Spectra Light Bulb
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Rule #2 Hot, transparent gas cloud Emission Spectra Neon Sign
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Rule #3 Hot, opaque solid with a cool gas cloud between the source and viewer Absorption Spectra The Sun
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Spectra Clues Looking at the spectrum of a star can help us identify what elements are in it Can also tell us about temperature and brightness Gives clues to hidden processes within the star
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Lots of Light “Light” is any EM wave EM= electromagnetic Has both an electric part and a magnetic part Not always “visible” to us Entire spectrum is huge
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Wave Anatomy Peak Trough Wavelength
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Length from one part of a wave to the next identical part Can be measured in any length unit Astronomers use Angstroms 1Å=.0000000001 meters (10 -10 m)
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Frequency f The # of waves that pass by a point in a given amount of time # of waves per second Measured in Hertz Hz
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Wavelength and Frequency Related! Long Wavelength = Low frequency Short Wavelength = High frequency Wavelength increases, frequency decreases
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Light Waves Wavelength x Frequency= Wave Speed x f = c (speed of light) c is same for every light wave So what separates them is frequency and wavelength
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Electromagnetic Spectrum There is a continuous spectrum of light Visible light (colors) are included in this They are only a very very small part
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EM Spectrum Gamma Rays X-rays Ultraviolet Visible Infrared Radio ← ← ← Wavelength increasing, Frequency decreasing
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Energy of Light Photons of light carry energy This energy is related to wavelength and frequency As frequency goes up, energy goes up, since more photons are arriving As wavelength goes up, energy goes down
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Energy of Light If you double frequency, you double energy Or, if you halve the wavelength, you double the energy
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Summary Light carries energy Atoms make light Light allows us to dissect objects that we can’t reach Wavelength, frequency, and energy of light are related
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