Post on 14-Jan-2016
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Radiation - Energy emitted in the form of waves (light) or particles (photons).
Beta Radiation: emits a beta particle (an electron). In beta decay a neutron in the nucleus changes into a proton, an electron and a neutrino and ejects the high speed electron (beta particle) from the nucleus..
Radioactive Emissions (Radiation)
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Radioactive Emissions (Radiation)
Penetrating Power
SymbolEquivalent
Description
Type
He Stopped by thick paper ()
Helium nucleus
Dense (+) charged particle
42
-1
-1
Stopped by 6mm of Al
High speed electron
(-) charged particle
e0
0
Alpha
Beta
Gamma
Stopped by several cm of Pb
High energy photons
Type of energy 0
0
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Beta Decay
When a parent nucleus decays by the Beta (β) decay process, an electron, called a beta particle (β) is emitted. The resulting daughter nucleus will always have the same atomic mass and an atomic number increased by one.
2863
2963
10Ni Cu e 28
632963
10Ni Cu e
emitted beta particle
atomic weight is constant
atomic number increases
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Beta Decay
epn 01
11
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Mass: 14 = 14 + 0 Charge: 6 = 7 + (-1)14 = 14 6 = 6
A beta particle is created in the nucleus by a process in which one neutron is transformed into a proton and an electron.
Example of Beta Decay:
14 14 076 -1C N e
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Beta Decay Application – Carbon Dating
Click here for a short video on carbon dating dead biological materials.
How old are these bones?
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Beta Decay Application – Carbon Dating
Carbon dating is a method of determining the age of dead biological materials based on the rate of decay of the radioactive isotope Carbon-14.
• Willard F. Libby pioneered carbon dating at the University of Chicago in the 1950's.
• In 1960, he won the Nobel Prize for Chemistry for this work.
• Radiocarbon dating is now the most widely used method of age estimation in the field of archaeology.
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Beta Decay Application – Carbon Dating
Carbon-14 begins when high-energy cosmic rays enter the earth's atmosphere. The rays collide with atoms to create a secondary cosmic rays in the form of an energetic neutron. (Every person on the earth is hit with about 500,000 cosmic rays every hour.)
atom
neutron cosmic ray
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These neutrons can then collide with the diatomic nitrogen molecules in the atmosphere. These collisions produce carbon-14 and nitrogen atoms, as well as protons.
neutron
Beta Decay Application – Carbon Dating
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Beta Decay Application – Carbon Dating
Just like carbon-12, carbon-14 chemically reacts with the oxygen in the atmosphere to produce carbon dioxide.
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Beta Decay Application – Carbon Dating
Almost all of the carbon dioxide in our atmosphere is derived from non-radioactive carbon-12 atoms. The ratio of normal carbon-12 to carbon-14 in the air and in all living things is nearly constant at any given time. This ratio is approximately 1 in every in one trillion carbon atoms is carbon-14.
1 Carbon-14
1,000,000,000,000 Carbon-12
14126
126
1.0 10C
xC
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Beta Decay Application – Carbon Dating
Like carbon dioxide made from xarbon-12, carbon dioxide made from carbon-14 enters the carbon cycle through photosynthesis.
As animals eat plant life they assimilate both carbon-12 and carbon-14 into their bodies in the ratio that carbon-12 and carbon-14 exist in nature.
The process of live organisms (including humans) taking in carbon continues until death.
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Beta Decay Application – Carbon Dating
Once an organism dies, it stops consuming Carbon and the amount of carbon-12 in the tissue remains constant.
But, the carbon-14 that was in the tissue radioactively decay (with a haf-life of 5,730 years) into nitrogen-14.
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Beta Decay Application – Carbon Dating
By measuring the ratio of c-12 to c-14 in a sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing.
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Beta Decay Application – Carbon Dating
The formula to calculate how old a sample is by carbon-14 dating is:
t = [ln(Nf/No)/(-0.693)]x t1/2
where:
ln is the natural logarithm
Nf/No is the percent of carbon-14 in the sample compared to the amount in living tissue
t1/2 is the half-life of carbon-14 (5,730 years)
1/ 2
ln( )
0.0693
f
o
N
Nt t