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

make atoms neutral?make atoms neutral?

Atomic modelsAtomic models

Plum pudding modelPlum pudding modelJ.J. ThomsonJ.J. Thomson

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

LasersLasers

CoherentCoherentMonochromaticMonochromaticDirectionalDirectionalUSESUSES

: measuring, cutting, reading music, : measuring, cutting, reading music, holograms, surgery holograms, surgery

RealityReality

Electrons don’t ‘orbit’ nicelyElectrons don’t ‘orbit’ nicelyElectron CloudElectron CloudHeisenberg’s Uncertainty PrincipleHeisenberg’s Uncertainty Principle

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

decay away.decay away.

Nuclear ReactionsNuclear Reactions

FissionFissionChain ReactionsChain ReactionsNuclear PowerNuclear PowerAtom bombsAtom bombs

FusionFusionStarsStarsDream energyDream energy

Other uses of radiationOther uses of radiation

medicine medicine chemotherapy chemotherapy power supplies power supplies plant mold killers. plant mold killers.

ForcesForces

StrongStrongWeakWeak

Faraday CageFaraday Cage

Dyson SphereDyson Sphere

RelativityRelativity

Time DilationTime Dilation

Length ContractionLength Contraction

Time TravelTime Travel

                                    

HomeworkHomework

Review for ExamReview for ExamMake 1 page of notes to useMake 1 page of notes to use