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Warm up. 1. What are some of the dangers of nuclear energy? 2. Where does the energy for nuclear reactions come from? (think of where the word “nuclear” comes from/sounds like). Atoms. Greeks: four elements Earth, fire, wind, water What’s the smallest piece you can cut something into?

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warm up
Warm up
  • 1. What are some of the dangers of nuclear energy?
  • 2. Where does the energy for nuclear reactions come from? (think of where the word “nuclear” comes from/sounds like)
atoms
Atoms
  • Greeks: four elements
    • Earth, fire, wind, water
    • What’s the smallest piece you can cut something into?
  • Late 1800’s ‘discover’ the atom as the smallest piece of stuff
    • Scientists new atoms were small, had mass, and were electrically neutral
electrons
Electrons
  • Scientists discovered the electron
  • They knew electrons had a negative charge, and were in the atom.
  • So where were the positive charges to make atoms neutral?
atomic models
Atomic models
  • Plum pudding model
    • J.J. Thomson
  • Solar system model
    • “The Bohr model” after N. Bohr
    • E. Rutherford experiment
energy levels
Energy levels
  • Electrons can only ‘orbit’ at certain levels of energy.
hydrogen atoms
Hydrogen Atoms
  • Orbital radius: rn = [h2n2] / [4(pi)2Kmq2]
  • n = orbital level
  • K = 9 * 109
  • h = Planck’s constant
  • q = electron charge
  • m = mass of an electron
energy of an electron
Energy of an electron
  • En = -13.6 eV * 1/n2
  • eV = electron volt
  • When an electron changes energy levels it goes up or down by this amount. This is Quantum physics: that means any photon emitted or absorbed by an atom has that energy.
slide8
Uses
  • Determining what stars are made of
  • Determining what is between earth and a star
lasers
Lasers
  • Light amplification by Stimulated Emission of Radiation
  • Excite an electron to a certain energy level (pump). Then it relaxes to a lower, stable, state. When it then jumps down to a its base state it releases a photon of the wavelength corresponding to the energy loss. E = hf
lasers1
Lasers
  • Coherent
  • Monochromatic
  • Directional
  • USES
    • : measuring, cutting, reading music, holograms, surgery
reality
Reality
  • Electrons don’t ‘orbit’ nicely
  • Electron Cloud
  • Heisenberg’s Uncertainty Principle
    • Can know where
    • Can know how much energy
    • Can’t know both
quantum tunneling
Quantum Tunneling
  • Example of electron cloud and statistical physics
light sabers
Light Sabers
  • Properties
    • Hot
    • Light
    • ~ 4 ft long
    • Deflect blaster bolts
other future weapons
Other future weapons
  • Rail guns
  • Coil Guns
radioactivity
Radioactivity
  • Alpha Decay – Helium Nucleus
  • Beta Decay – Electrons emitted from the nucleus when a neutron turns into a proton
  • Gamma decay – photon emission from nucleus.
  • ½ life – time it takes for half a substance to decay away.
nuclear reactions
Nuclear Reactions
  • Fission
    • Chain Reactions
    • Nuclear Power
    • Atom bombs
  • Fusion
    • Stars
    • Dream energy
other uses of radiation
Other uses of radiation
  • medicine
  • chemotherapy
  • power supplies
  • plant mold killers.
forces
Forces
  • Strong
  • Weak
relativity
Relativity
  • Time Dilation
  • Length Contraction
  • Time Travel
homework
Homework
  • Review for Exam
  • Make 1 page of notes to use
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