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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. Greeks: four elements Earth, fire, wind, water What’s the smallest piece you can cut something into?

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Warm up

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  1. 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)

  2. 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

  3. 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?

  4. Atomic models • Plum pudding model • J.J. Thomson • Solar system model • “The Bohr model” after N. Bohr • E. Rutherford experiment

  5. Energy levels • Electrons can only ‘orbit’ at certain levels of energy.

  6. 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

  7. 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.

  8. Uses • Determining what stars are made of • Determining what is between earth and a star

  9. 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

  10. Lasers • Coherent • Monochromatic • Directional • USES • : measuring, cutting, reading music, holograms, surgery

  11. Reality • Electrons don’t ‘orbit’ nicely • Electron Cloud • Heisenberg’s Uncertainty Principle • Can know where • Can know how much energy • Can’t know both

  12. Quantum Tunneling • Example of electron cloud and statistical physics

  13. Light Sabers • Properties • Hot • Light • ~ 4 ft long • Deflect blaster bolts

  14. Other future weapons • Rail guns • Coil Guns

  15. 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.

  16. Nuclear Reactions • Fission • Chain Reactions • Nuclear Power • Atom bombs • Fusion • Stars • Dream energy

  17. Other uses of radiation • medicine • chemotherapy • power supplies • plant mold killers.

  18. Forces • Strong • Weak

  19. Faraday Cage

  20. Dyson Sphere

  21. Relativity • Time Dilation • Length Contraction • Time Travel

  22. Homework • Review for Exam • Make 1 page of notes to use

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