Warm up
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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

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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?

  • Late 1800’s ‘discover’ the atom as the smallest piece of stuff

    • Scientists new atoms were small, had mass, and were electrically neutral


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

  • Plum pudding model

    • J.J. Thomson

  • Solar system model

    • “The Bohr model” after N. Bohr

    • E. Rutherford experiment


Energy levels

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


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

  • 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.


Uses

  • Determining what stars are made of

  • Determining what is between earth and a star


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


Lasers

  • Coherent

  • Monochromatic

  • Directional

  • USES

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


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

  • Example of electron cloud and statistical physics


Light Sabers

  • Properties

    • Hot

    • Light

    • ~ 4 ft long

    • Deflect blaster bolts


Other future weapons

  • Rail guns

  • Coil Guns


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

  • Fission

    • Chain Reactions

    • Nuclear Power

    • Atom bombs

  • Fusion

    • Stars

    • Dream energy


Other uses of radiation

  • medicine

  • chemotherapy

  • power supplies

  • plant mold killers.


Forces

  • Strong

  • Weak


Faraday Cage


Dyson Sphere


Relativity

  • Time Dilation

  • Length Contraction

  • Time Travel


Homework

  • Review for Exam

  • Make 1 page of notes to use


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