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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.
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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