Radiation

What is Radiation?

Radiation is the energy emitted by atoms that are unstable.  There are both natural and man-made forms of radiation.  Natural radiation, which is about 85% of where our exposure to radiation comes from is found in from potassium in our food, to the uranium and radium in the soil to the sun.  Man-made radiation, which accounts for the rest of the 15% comes from the television to the x-rays we take at the orthopedic or the dentist. 

So how do these atoms become stable?

An atom is unstable because it is going through a process called decaying, which in course of this  process it emits radiation in forms of rays and/or particles before it finally becomes stable.  The length of the decaying process varies among the isotopes and depends on the atom, though it can range from billions of years to fractions of seconds (for example, uranium).  While no one knows exactly when the element will decay, there is a pattern on how long it takes the atom to reach it's half life, where half of its atoms decay.  Which in turn takes that long to decay half of the atoms that are left and so on.

What types of radiation is emitted?

While there are several different types of radiation being emitted, there are four principle types ones from the decay of radioactive isotopes are: alpha particles, beta particles, gamma rays, and neutrons 

Alpha Particles

An alpha particle is a positively charged particle that is emitted in the radioactive decay of some unstable atoms.  It is made up of two protons and two neutrons (essentially like a helium atom).  Because of it's size, it is heavier and slower-moving than other emissions of the radioactive decay.  Alpha particles do not penetrate far into a material and can be stopped quite easily, for example by a sheet of paper.   However, they are capable of breaking chemical bonds when they strike a molecule because of their size, mass and charge and therefore can cause biological and chemical damage.  Since penetration by the alpha particle depends on where the particle is being released and what is the barrier, they are mostly damaging if they are ingested or inhaled into the lungs.

Beta Particles

A beta particle is another particle that is emitted during a radioactive decay of some unstable atoms.  They can be either positively (usually called a positron) or negatively charged (usually called either a negatron or an electron) and have a very small mass, about 1/2000 of the mass of a neutron.  Most negatively charged beta particles occur from natural occurring radioactive decay, while positively charged beta particles occur from man-made radioactive decay.   Beta particles can penetrate farther than alpha particles, though that depends again on where the particle is released and what type of material is being penetrated.  However, they can be stopped fairly easily by a sheet of aluminum.  The difference between positrons and electron is that positrons are less penetrating than electrons because they interact with an electron and both particles are annihilated.  Since beta particles can penetrate the skin (and several layers of tissue), it is considered both an external and internal hazard, though people can be shielded from beta radiation by the use of layers of metals and plastics.

Gamma Rays

Gamma rays are a type of very strong electromagnetic wave and it has no weight and travels at the speed of light (about 3.00 x 10⁸ m/s).  Therefore compared to alpha particles and beta particles it is much more faster and penetrating.  It is emitted when a nucleus transmissions from a higher energy level to a lower energy level.  Also, another type of electromagnetic radiation needs to be mention here are x-rays which are emitted by an atomic electron changing energy levels.  The penetration level of gamma ray is reduced by the intensity and distance of the penetration.  Low intensity of gamma radiation can  damage living cells and cause cancer, while high level of gamma radiation can kill cells.  Therefore, to shield from gamma radiation, several feet of materials like concrete and lead is needed to prevent penetration.  This is also why gamma radiation is used in treatment for cancer called radiotherapy, in which the cancer cells are targeted by a beam of gamma radiation.

Neutrons

Free neutrons outside of an atom are unstable and usually have a half-life of ten minutes.  They weigh about 1/4 the mass of an alpha particle but 2000 times larger than that of a beta particle. Since it has no charge and it only reacts the atoms nuclei, it can penetrate further than charged particles and it is very hard to determine it's location.  Since they play an important role in nuclear fission, nuclear reactors are designed to produce lots of free neutrons since they sustain the nuclear fission chair  reaction (an important part in generating nuclear power).    It is considered a health hazard like gamma radiation, and maybe even more so because one of the hazards is neutron activation, which is the ability of neutron radiation to induce radioactivity in most substances it encounters.  This includes body tissues of the people who interact with it.  In addition that is why this process accounts for much of the radioactive material that is released during a detonation of a nuclear weapon.  Protection from neutron radiation depends on radiation shielding that is based on charged particles so that the neutrons are absorbed by a light nuclei (for example hydrogen).  The most effective materials are water, polyethylene, paraffin wax, or concrete-in which a large amount of water is chemically bound to it. 

So you mean there's this harmful stuff just floating around ready to fry my cells?

Well there is radiation everywhere as I mentioned earlier from the sun to the stuff we eat, but don't start worrying quite yet.  Most of the levels of radiation we encounter is safe with little impact on us.   There are possible ways to encounter radiation that can be potentially lethal and life-threatening.  But it is most likely rare that the nuclear power plant in your city is going to have a melt-down so don't start panicking.  However, the US government controls the access to radiation very carefully as well as tries to lower the exposure to radiation.  The nuclear safety record is pretty good compared to the hazardous waste records.  Yet, if you end up working in a lab with radioactive materials take all precautions to keep yourself safe!

So far this has sounded pretty bad...is there any good side to radiation?

There is plenty of benefits associated with radiation, like earlier mentioned under gamma radiation, which helps treat cancerous cells (even though it can cause cancer as well in normal cells in high intensity radiation).  But radiation helps diagnose illnesses by the use of x-rays and treat illnesses such as hyperthyroidism and cancer.  Radiation helps kill bacteria, as well as preserve food  without chemicals and refrigeration.   It's plays an important role in making things like smoke detectors to even making ice cream.  In addition it helps prove authenticity of documents and works of art to help figure out the age of ancient objects through carbon dating.  There are so many different ways radiation helps us in our day to day lives that it would be very hard for me to list here.  However, if you go back to the main page you can learn about one of the most important ways radiation helps us, which is through nuclear power.