1 / 18

Forces in the nucleus

Forces in the nucleus. 3 forces Electromagnetic (+ protons and – electrons) Strong nuclear forces (hold together nucleus) Weak nuclear forces (beta decay). What is radioactivity?. Unstable nucleus Emits particles or energy To become stable The nucleus of uranium-238 is radioactive.

nonnie
Download Presentation

Forces in the nucleus

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. Forces in the nucleus • 3 forces • Electromagnetic (+ protons and – electrons) • Strong nuclear forces (hold together nucleus) • Weak nuclear forces (beta decay)

  2. What is radioactivity? • Unstable nucleus • Emits particles or energy • To become stable • The nucleus of uranium-238 is radioactive. • Emits radiation (particles) • Transforms into a stable atom • Uranium-238 lead-206 • Takes about 5 billion years

  3. Unstable isotopes emit 3 kinds of radioactive decay • Alpha decay • 2 protons & 2 neutrons released • Called alpha particle • Beta decay • Neutron splits into a proton and an electron • The proton stays in the nucleus but the electron is emitted – beta particle • Gamma decay • Release of high-energy, electromagnetic radiation from the nucleus of an atom

  4. http://www.gcsescience.com/prad17-measuring-half-life.htm Half-life (nuclear reactions lab) • Length of time for half a sample of radioactive material to decay

  5. Station A – Half life • What type of decay has Cesium undergone? • β • How do you know? • Mass unchanged, atomic number increased by 1 (neutron turned into a proton + electron) • If you started with 60 grams of Cesium-137, how many grams would be remaining after 30 years? 30 grams 60 years? 15 grams 90 years? 7.5 grams • How long would it take to decay 90% of the Cesium-137? • Between 90-120 years

  6. B Questions • A radioactive substance has a half-life of 30 minutes. What fraction of the atoms will not have decayed after 1 hour? • 1/4 • Another substance has a half-life of 3 hours. What fraction of the atoms will have decayed after 6 hours? • 3/4 • A researcher measures 200 counts per minute coming from a radioactive source at midday.At 3 o'clock, she finds that this has dropped to 25 counts per minute.What is the half-life of the radioactive source? • 1 hour

  7. C Questions • What is the isotope? • Sodium-24 • Using this graph, determine the ½ life of the substance shown. • 14-15 hours • How much radioactive substance is remaining after 30 hours? • 100 counts per second • How much radioactive sample has decayed after 60 hours? • 400-24=376 counts per second • How many neutrons are in this isotope of sodium? • 13

  8. m

  9. Nuclear reactions • Fission • Split one atom to make 2 • Fusion • Fuse 2 atoms to make one +

  10. Nuclear fusion in the sun

  11. light Wave or Particle? • Thomas Young’s double slit experiment • Interference pattern • Diffraction • Interference • http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/ • Photoelectric effect • High energy photons bounce off • Photon – particle with no mass • http://www.lpscience.fatcow.com/mgagnon/Photoelectric_Effect/photoelectriceffect1.htm

  12. Photoelectric effect proved light travels as a particle • Blue light • Red light • Light particles are called photons • No mass therefore no momentum • Travel at near speed of light • A photon does not obey the laws of conservation of mass & energy

  13. Thomas Young’s experimentproved light travels as a wave http://www.cavendishscience.org/phys/tyoung/tyoung.htm http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/ http://vsg.quasihome.com/interfer.htm http://video.google.com/videoplay?docid=-4237751840526284618

  14. Quantum model of the atom • Predicts only probability of location of the electrons in orbitals • http://science.howstuffworks.com/atom8.htm Bohr Model of Atom

  15. Heisenberg Uncertainty Principle http://www.aip.org/history/heisenberg/p08.htm • Both momentum and position cannot be known when dealing with subatomic particles • You can know one, but not both!

  16. What is space-time?And how does it get warped? Space-time is the combination of 3 dimensions of space and 1 dimension of time and can be warped or distorted by large masses

  17. Light bending due to warping of space-time

  18. Twin paradox • http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/ • Time dilatation • http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm

More Related