Atomic, Nuclear, and Particle Physics (Part 2):
Half-Life. The HALF-LIFE of a radioisotope is the amount of time it takes for half of the sample to decay. A DECAY CURVE is a graph of the decay of a radioisotope (amount vs. time). Some radioisotopes have long half-lives.For other radioisotopes, the half-life can be short. Note: Chart displays average values of half-life for common isotopes.
A(T) = Ao2-T/t T/t = n, number of half-lives Note: Chart displays average values of half-life for common isotopes. Note: Chart displays average values of half-life for common isotopes. Chart based on individual isotopes, with average half-life estimates.
Radio-Isotopes Used in Medicine Chart based on individual isotopes, with average half-life estimates. Fission and Fusion: FISSION is splitting a big atom into two
smaller atoms by bombarding with neutrons. Energy is released according to Einsteins equation: E = mc2.E is energy, m is mass, c is speed of light. The fission process can continue until all of the available big atoms are gone.This is a CHAIN REACTION. A Nuclear Fission Reaction.
Unstable More Unstable + 200 MeV A Nuclear Fission Reaction. Uranium 235, struck with a neutron, and split into Krypton and Barium
A Chain Reaction Chain Reaction: Uranium 235, struck with a neutron, and split into Krypton and Barium Fission and Fusion: FUSION is the combining of two small atoms into one bigger atom with release of energy. More energy is released than fission. Occurs continuously in the sun and stars Requires temperature of 100,000,000C Problem to reach and maintain this temp Good source of future energy lots of H in ocean Waste products decay much faster than fission NUCLEAR FUSION : Joining atoms.
1H2 + 1H He4 + 0n MeV Nuclear Power: This is a fission reaction.Mass of uranium is kept small and CONTROL RODS absorb neutrons to prevent chain reaction. Problems are: Public perception Security Hazardous radioactive waste that has half-life of thousands of years *storage 2150 ft underground in NM 10% of power in US from nuclear power A Nuclear Reactor Used to Boil Water for a Steam Turbine
( A Nuclear Reactor Used to Generate Electricity What Happened at Chernobl.
1. Steam Explosion. 2. Partial Meltdown. 3. Containment held. Radioactivity: Overview of Units
Activity:Becquerel (Bq) = 1 decay / s 1 curie (Ci) = 3.71010 decays / s (or Bq) (disintegration rate of 1g of radium) Ion Dose:Ionizing behavior of radiation is most damaging tous!Roentgen = 2.6104 C/ kgair(or J/kg) Energy Dose:rad= J/kg Energy Dose for Human Health Considerations: rem = # rads quality factor (a = 10 and b, g= 1) Dosages: rem / yr = natural background rem / yr = limit for nuclear power plant workers rem = LD50 (50% die within a month) 750 rem = fatal dose (5000 rem = fatal within 1 week) Particle detectors: Photographic Film. Scintillation Screen.
Gieger-Muller Tube. Cloud Chamber. Bubble Chamber. The Nobel Prize in Physics 1939
Awarded to E.O. Lawrence, Univ. of California, Berkeley "for the invention and development of the Cyclotron and for results obtained with it, especially with regard to artificial radioactive elements" The Linear Accelerator was invented by John Cockcroft and E. T. S
The Linear Accelerator was invented by John Cockcroft and E. T. S. Walton at the Cavendish Laboratory, Cambridge, England, in the late 1920s Known Elementary Particles
Symbol Charge Mass (amu) Proton p, 1H1 +1 Neutron n Electron -1e0 , - -1 Alpha 2He4, +2 4.0026 Positron +1e0 , + Neutrino Quark , +2/3 , -1/3 u d The Discovery of Quarks!
up down The Building Blocks of Protons and Neutrons. Charge Q +2/3 -1/3 Mass ~5 [MeV/c2] ~10 [MeV/c2] u d Note: The neutron differs from a proton only by d u quark replacement! Proton Neutron u u d d u d Q = +1 M=938 MeV/c2 Q = 0 M=940 MeV/c2