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 come from? (think of where the word “nuclear” comes from/sounds like) 2. Where does the energy for nuclear reactions come from? (think of where the word “nuclear” comes from/sounds like)

Atoms Greeks: four elements Greeks: four elements Earth, fire, wind, water Earth, fire, wind, water What’s the smallest piece you can cut something into? What’s the smallest piece you can cut something into? Late 1800’s ‘discover’ the atom as the smallest piece of stuff Late 1800’s ‘discover’ the atom as the smallest piece of stuff Scientists new atoms were small, had mass, and were electrically neutral Scientists new atoms were small, had mass, and were electrically neutral

Electrons Scientists discovered the electron Scientists discovered the electron They knew electrons had a negative charge, and were in the atom. They knew electrons had a negative charge, and were in the atom. So where were the positive charges to make atoms neutral? So where were the positive charges to make atoms neutral?

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

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

Hydrogen Atoms Orbital radius: r n = [h 2 n 2 ] / [4(pi) 2 Kmq 2 ] Orbital radius: r n = [h 2 n 2 ] / [4(pi) 2 Kmq 2 ] n = orbital level n = orbital level K = 9 * 10 9 K = 9 * 10 9 h = Planck’s constant h = Planck’s constant q = electron charge q = electron charge m = mass of an electron m = mass of an electron

Energy of an electron E n = eV * 1/n 2 E n = eV * 1/n 2 eV = electron volt 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. 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 stars are made of Determining what is between earth and a star Determining what is between earth and a star

Lasers Light amplification by Stimulated Emission of Radiation 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 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 Coherent Monochromatic Monochromatic Directional Directional USES USES : measuring, cutting, reading music, holograms, surgery : measuring, cutting, reading music, holograms, surgery

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

Quantum Tunneling Example of electron cloud and statistical physics Example of electron cloud and statistical physics

Light Sabers Properties Properties Hot Hot Light Light ~ 4 ft long ~ 4 ft long Deflect blaster bolts Deflect blaster bolts

Other future weapons Rail guns Rail guns Coil Guns Coil Guns

Radioactivity Alpha Decay – Helium Nucleus Alpha Decay – Helium Nucleus Beta Decay – Electrons emitted from the nucleus when a neutron turns into a proton Beta Decay – Electrons emitted from the nucleus when a neutron turns into a proton Gamma decay – photon emission from nucleus. Gamma decay – photon emission from nucleus. ½ life – time it takes for half a substance to decay away. ½ life – time it takes for half a substance to decay away.

Nuclear Reactions Fission Fission Chain Reactions Chain Reactions Nuclear Power Nuclear Power Atom bombs Atom bombs Fusion Fusion Stars Stars Dream energy Dream energy

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

Forces Strong Strong Weak Weak

Faraday Cage

Dyson Sphere

Relativity Time Dilation Time Dilation Length Contraction Length Contraction Time Travel Time Travel

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