Warm up Warm up 1. What are some of the dangers 1. What are some of the dangers of nuclear energy? of nuclear energy? 2. Where does the energy for 2. Where does the energy for nuclear reactions come from? nuclear reactions come from? (think of where the word (think of where the word “nuclear” comes from/sounds “nuclear” comes from/sounds like) like)
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Warm up 1. What are some of the dangers of nuclear energy? 1. What are some of the dangers of nuclear energy? 2. Where does the energy for nuclear reactions.
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Warm upWarm up
1. What are some of the dangers of 1. What are some of the dangers of nuclear energy?nuclear energy?
2. Where does the energy for nuclear 2. Where does the energy for nuclear reactions come from? (think of where the reactions come from? (think of where the word “nuclear” comes from/sounds like)word “nuclear” comes from/sounds like)
AtomsAtoms
Greeks: four elementsGreeks: four elementsEarth, fire, wind, waterEarth, fire, wind, waterWhat’s the smallest piece you can cut What’s the smallest piece you can cut
something into?something into?Late 1800’s ‘discover’ the atom as the Late 1800’s ‘discover’ the atom as the
smallest piece of stuffsmallest piece of stuffScientists new atoms were small, had mass, Scientists new atoms were small, had mass,
and were electrically neutraland were electrically neutral
ElectronsElectrons
Scientists discovered the electronScientists discovered the electronThey knew electrons had a negative They knew electrons had a negative
charge, and were in the atom.charge, and were in the atom.So where were the positive charges to So where were the positive charges to
Solar system modelSolar system model ““The Bohr model” after N. BohrThe Bohr model” after N. BohrE. Rutherford experimentE. Rutherford experiment
Energy levelsEnergy levels
Electrons can only ‘orbit’ at certain levels Electrons can only ‘orbit’ at certain levels of energy. of energy.
Hydrogen AtomsHydrogen Atoms
Orbital radius: rOrbital radius: rnn = [h = [h22nn22] / [4(pi)] / [4(pi)22KmqKmq22]]n = orbital leveln = orbital levelK = 9 * 10K = 9 * 1099
h = Planck’s constanth = Planck’s constantq = electron chargeq = electron chargem = mass of an electronm = mass of an electron
Energy of an electronEnergy of an electron
EEnn = -13.6 eV * 1/n = -13.6 eV * 1/n22 eV = electron volteV = electron voltWhen an electron changes energy levels it When an electron changes energy levels it
goes up or down by this amount. This is goes up or down by this amount. This is Quantum physics: that means any photon Quantum physics: that means any photon emitted or absorbed by an atom has that emitted or absorbed by an atom has that energy. energy.
UsesUses
Determining what stars are made ofDetermining what stars are made ofDetermining what is between earth and a Determining what is between earth and a
starstar
LasersLasers
Light amplification by Stimulated Emission Light amplification by Stimulated Emission of Radiationof Radiation
Excite an electron to a certain energy level Excite an electron to a certain energy level (pump). Then it relaxes to a lower, stable, (pump). Then it relaxes to a lower, stable, state. When it then jumps down to a its state. When it then jumps down to a its base state it releases a photon of the base state it releases a photon of the wavelength corresponding to the energy wavelength corresponding to the energy loss. E = hf loss. E = hf
Can know whereCan know whereCan know how much energyCan know how much energyCan’t know bothCan’t know both
Quantum TunnelingQuantum Tunneling
Example of electron cloud and statistical Example of electron cloud and statistical physicsphysics
Light SabersLight Sabers
PropertiesPropertiesHotHotLightLight~ 4 ft long~ 4 ft longDeflect blaster boltsDeflect blaster bolts
Other future weaponsOther future weapons
Rail gunsRail gunsCoil GunsCoil Guns
RadioactivityRadioactivity
Alpha Decay – Helium NucleusAlpha Decay – Helium NucleusBeta Decay – Electrons emitted from the Beta Decay – Electrons emitted from the
nucleus when a neutron turns into a protonnucleus when a neutron turns into a protonGamma decay – photon emission from Gamma decay – photon emission from
nucleus. nucleus. ½ life – time it takes for half a substance to ½ life – time it takes for half a substance to