or
spend weeks behind glass (which cuts out the UV, but lets through the visible
light) without a tan.Photons effect depends on their energy, which increases as the wavelength is shorter (higher frequency)
c = f l E = h f
Amount of radiation depends on the intensity (i.e. the number of photons).
Example: You can get a sunburn in 20 minutes
or
spend weeks behind glass (which cuts out the UV, but lets through the visible
light) without a tan.
B) Streams of Particles
(with rest mass traveling at various speeds)
C) Radioactive Disintegration
E) External Exposure to Radiation
(clay)F) Art Forgery Detection & Other Crime Detection
I) Other Uses of Radiation in Everyday Life
J) Nuclear Accidents
K) Atomic Bomb
Nuclear Chemistry deals with the nuclei
of atoms breaking apart. Atoms
are continually undergoing decay. When studying nuclear chemistry, there is
a typical format used to represent specific isotopes.
Where A is the parent
isotope (the atom being broken apart) B is the daughter
isotope or the isotope formed. When an element
is broken down in alpha decay it looses two neutrons and two (2) protons.
This means that the name of the element will change as well, moving back two
(2) places on the periodic table. Alpha decay is is not very penetrating
because the He atoms capture electrons before traveling very far. However it
is very damaging because the alpha particles can knock atoms off of molecules.
Alpha
decay is the most common in elements with an atomic number greater than 83.
The beta emission increases the atomic
number by one (1) by adding one (1) proton. At the same time, one (1) neutron
is lost so the mass of the daughter isotope is the same as the parent
isotope. Beta negative decay is more penetrating than alpha decay because
the particles are smaller, but less penetrating than gamma decay. Beta
electrons can penetrate through about one (1) cm of flesh before they are
brought to a halt because of electrostatic
forces. Beta decay is most common in elements with a high neutron to
proton ratio.
In gamma emission, neither the atomic number or the
mass number is changed. A very highly charged gamma ray is given off when
the parent isotope falls into a lower energy state. Gamma radiation is the
most penetrating of all. These photons can pass through the body and cause
damage by ionizing all the molecules in their way.
In this reaction a positron is emitted. A positron is
exactly like an electron in mass and charge force except with a positive
charge. It is formed when a proton breaks into a neutron with mass and no
charge and this positron with no mass and the positive charge. Positron
emission is most common in lighter elements with a low neutron to proton
ratio.
In this reaction a nucleus captures one (1) of its own atom's inner shell electrons which reduces the atomic number by one. This captured electron joins with a proton in the nucleus to form a neutron. Electron capture is common in larger elements with a low neutron to proton ratio.
All elements with an atomic number over 83 are considered radioactive. Radioactivity can be measured using a geiger counter, a cylinder containing a low-pressure gas and two (2) electrodes. Radiation ionizes the atoms in the cylinder and allows current to flow between the electrodes.
All radioactive elements disintegrate according to their specific half life. The half life of a radioactive substance is the time required for half of the initial number of nuclei to disintegrate. The decay rate expresses the speed at which a substance disintegrates. The following equation represents the relationship between the number of nuclei remaining, N, the number of nuclei initially present, NO, the rate of decay, k, and the amount of time, t.
The relationship between the half-life of a radioactive substance and k, the rate at which it decays can also be found.
By using these equations, it is possible to calculate how much of a nuclear substance will be left after a certain time and how much of a substance originally existed. A common example is isotopic dating in which the ages of archeological artifacts are determined by measuring the activity of the isotopes. The variable n is the number of half-lifes.
2. If a watch contains a radioactive substance with a decay rate of 1.40 * 10 -2 and after 50 years only 25 mg remain, calculate the amount originally present. Solution.
3. A rock contains 0.257 mg of lead-206 for every mg of uranium-238. The half-life decay for uranium to turn into lead is 4.5x109 yr. How old is the rock? Solution.
Breeding Pu-239 from U-238
Source of graphic: http://www.ccnr.org/breeding_ana.html
A Nuclear Calculator and a Disintegration Time Calculator are available for use.
Government Agency Web sitesRadiation Topics Plutonium Properties
Nuclear Energy Timeline PowerPoint
Useful Background Animated Wavefronts
Famous Nuclear Scientists Vocabulary HW
Help Files for Nuclear Chemistry
Nuclear Experiments Cs-137 EPA sight Radiation Fact Sheet
Glossary of Nuclear Terms Glossary
The Living Textbook of Nuclear Chemistry
The Pros and Cons of Nuclear Energy
Alpha Radiation in Lung Tissue of Ape
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