1 / 14

Nuclear Physics

E = mc 2. Nuclear Physics. Outline. Theory of Special Relativity Postulates E = mc 2 The Atom What makes up the atom? What holds the atom together? Quantum Physics. The theory of Special Relativity. Galilean relativity: To car A, car B is going 100 – 20 = 80m/s.

mireya
Download Presentation

Nuclear Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. E = mc2 Nuclear Physics

  2. Outline Theory of Special Relativity Postulates E = mc2 The Atom What makes up the atom? What holds the atom together? Quantum Physics

  3. The theory of Special Relativity Galilean relativity: To car A, car B is going 100 – 20 = 80m/s. Special relativity: Light moves at v = c for all observers v = 100 m/s b v = 20 m/s a v = .9 c v = c

  4. Consequences of Relativity Due to Einstein: 1905 Length contraction: Objects moving near the speed of light appear shorter Time dilation: Clocks moving near the speed of light appear to be running slow. No object having mass can move at c. Rest energy: E = mc2

  5. E = mc2 All laws of nature must hold, regardless of how fast or slow the observer is moving. Energy conservation is a law of nature. Einstein predicted that, in order for Energy Conservation to hold, there must be a certain amount of energy associated with mass, called the “Rest Energy” = mc2.

  6. What does it mean? It means that all matter can theoretically be converted into energy. Example: My mass is 70 kg. My rest energy is E = (70 kg) (3 x 108 m/s)2 E = 6.3 x 1018 J = 6 x 1015 Btu! My rest energy is about 5% of the energy consumed per year in the US! Matter is equivalent to energy.

  7. Atoms: the constituents of matter An atom: Protons and electrons are charged oppositely, having 1.6 x 10-19 C The type of atom is determined by Z = the number of protons. Electrons (-e) in orbit Central nucleus of Protons (+e) and neutrons

  8. The atomic nucleus m electron = 9.11 x 10-31 kg E = (9.11 x 10-31 kg) c2 = 8.2 x 10-14J Convert to units of eV. m electron = .511 MeV m proton = 938.26 MeV m neutron = 939.55 MeV. The nucleus has the most mass, and therefore the most available energy.

  9. Isotopes The kind of atom is determined by Z The number of neutrons, N, can vary. Atoms having the same Z but different N are called: ISOTOPES.

  10. Chart of Nuclear Isotopes

  11. Nuclear stability Not all isotopes are equal Range of stability Z < 40 is ZN Z > 40, N > Z Isotopes which are NOT stable experience RADIOACTIVE DECAY.

  12. Nuclear Decay Alpha decay: The nucleus expels two protons and two neutrons – an alpha particle. Beta decay: The nucleus expels one electron (a beta particle), and a neutron in the nucleus turns into a proton! Gamma decay: The nucleus expels a high energy photon – a gamma particle. Fission: A large nucleus, like Uranium, splits into two smaller nuclei, releasing several neutrons.

  13. A HOT Nucleus. Many kinds of decay, but all of them release a lot of energy! For comparison: The energy of a visible light photon is 1-3 eV The energy released per nuclear decay is anywhere from 100 keV to 100 MeV in fission. The energy comes from lost nuclear mass!

  14. Neutron decay A neutron will spontaneously turn into a proton, electron and a neutrino (anti-). The mass of the products is .78 MeV less than the mass of the neutron! That energy is released as heat.

More Related