I'm not sure how saying "travel" to refer to energy being emitted from one object to another instead of "transfer" is dangerously misleading. I'm not a physics major but I feel I wouldn't be kicked out of science class for referring to the sun's radiation as traveling to Earth instead of transferring to it. Also, this is probably best taken up with Wikipedia and "In physics, radiation describes a process in which energetic particles or waves travel through a medium or space."

I'm aware floating about is the not the best description, but that sort of thing happens in an effort to heavily simplify a description.

No, you wouldn't, but you most probably would at least be met with a weird expression on the professor's face if you said that energy travels from Sun to Earth. Radiation transfers energy by travelling - energy is transferred, radiation is travelling.


Yes - particles travel, transferring energy in the process.

A detailed explanation of that would require some pretty deep forays into quantum mechanics, which is way beyond my pay grade (and probably the pay grades of everyone else here as well, unless we have nuclear physicists or engineers in the community).

"Radioactive materials" (i.e. uranium, thorium, plutonium, etc.) are made up of atoms which are unstable, and they will spontaneously break down into atoms which are more stable, releasing pieces of themselves (particles) as well as ionizing energy (i.e. "radiation"). How quickly they break down is a function of their energy and quantum states, and is expressed by the term half-life. The half-life of a material is simply a measure of how long it would take for, say, one gram of the material to transform itself into one half gram of the original material plus one half gram of the more stable types it wants to break down into. This varies widely with different materials - there are some with half-lives measured in billionths of a second, while Uranium-238 has a half-life of 4.5 billion years.

In the case of the atomic bomb tests, the blast vaporized an enormous amount of matter that was caught in it, turning it into dust, and this dust was svcked up into the center of the blast, got all kinds of different radioactive particles (with all kinds of half-lives) attached to it, and then settled back to earth, contaminating the soil and water in the area. This is seen as the infamous "mushroom cloud" of atomic explosions, and the radioactive dust that settled is what "fallout" actually is.

Actually, all those things are not forms of "light". They are various wavelengths in the electromagnetic spectrum of which light is one kind, and is the kind we can see. Radio waves are the lowest energy waves in the electromagnetic spectrum, then Microwaves, then Infrared (Heat), then visible light, then ultraviolet, then x-rays, and then lastly are Gamma rays.

Also just so everyone knows, microwaves used by cell phones to send signals do not cause cancer. It is only the stuff beyond the wavelength of light that can do that. I imagine microwaves would be classified as non-ionizing from what I read here.

maybe

To expand a bit on this, the various types of radiation carry different amounts of energy, which correspond to different atomic and molecular transitions in energy states. At the low energy side of things you have radio waves, which correspond with nuclear spin transitions in atoms. Microwaves are a bit more energetic and correspond to changes in the rotational states of molecules. Infrared is a bit more energetic still and corresponds to changes in the vibrational states of molecules. From there it goes to visual light and low energy UV light, which correspond to changes in the energy states of electrons, but not enough of a change to fully remove an electron from a molecule or break a chemical bond. However, once you get to higher energy UV light, X-rays, gamma rays, and so forth you're now dealing with enough energy to fully remove electrons from molecules (hence the "ionizing" radiation), as well as breaking chemical bonds (this is the primary danger of ionizing radiation, due to the formation of highly reactive radicals which then react with various molecules in our bodies, such as DNA).

As for alpha and beta particles vs gamma radiation, the difference is not so much one of energy (as all forms can vary quite a bit in total energy and all overlap), but rather one of penetrating power. Alpha particles are the most massive, so interact the most easily with matter and as a result have very little penetrating power (clothing and just your skin are often sufficient to stop alpha particles). Beta particles are much less massive and thus require more shielding to stop (although even the most energetic beta particles can still be stopped by just a few mm of metal shielding). Gamma radiation is massless and thus the most difficult to stop, and is where you'll need a fair amount of very dense shielding material (such as lead, or several meters of concrete).

The measures of radiation that most people are familiar with (rads and rems) actually are a measure of absorbed radiation. Rads are a measure of absorbed energy per unit mass (1 rad = 100 ergs absorbed by 1 g of matter), while a rem is a measure of rads adjusted by a weighting factor that corresponds to how much damage the particular type of radiation is capable of doing to mammalian tissue.

In physics, radiation describes a process in which energetic particles or waves travel through mass or space. There are two distinct types of radiation (as has been mentioned a few times now); ionizing and non-ionizing, though the word radiation is commonly used in reference to ionizing (i.e., having sufficient energy to ionize an atom) radiation only (this would essentially be the case with Fallout, which is where you question stems from) but it may also refer to non-ionizing radiation (e.g., radio waves or visible light) as well. The energy radiates (i.e., travels outward in straight lines in all directions) from its source, and this geometry naturally leads to a system of measurements and physical units that are equally applicable to all types of radiation. What has been misstated a few times here though, is that both ionizing and non-ionizing radiation can be harmful to organisms and can result in changes to the natural environment.

As previously mentioned, radiation with sufficiently high energy can ionize atoms - most often this occurs when an electron is stripped (or knocked out) from an electron shell which leaves the atom with a net positive charge. Because cells are made of atoms, this ionization can result in the formation of cancer. The probability of ionizing radiation causing cancer varies from case to case, and is dependent upon the dose rate of the radiation and the sensitivity of the organism.

The energy of non-ionizing radiation is less, and instead of producing charged ions when passing through matter the electromagnetic radiation has only enough energy to change the rotational, vibrational or electronic capacity levels of molecules and atoms. The effect of non-ionizing forms of radiation on living tissue have only recently been studied. Nevertheless, different biological effects are observed for different types of non-ionizing radiation.

Of course, most of that has been pointed out already across the assorted posts in the thread, so probably redundant of me to have posted.

Found this on the Wiki. I just copied the first sentence because everything after that was complicated and not easy to understand.

"In physics, radiation describes a process in which energetic particles or waves travel through a medium or space." So the best way I can think of it, is... Think of radiation as Heat. Like it gives out heat rays. I believe everything gives of radiation, most of it non leathel, so think of it as everything gives of heat or heat rays. . (just for the sake of argument.) So a pencil is cold so it doesn't give out alot of radiation. A lead plate is cold and does not give off radiation. Fire gives off radiation, it gives off alot of heat. The sun gives off radiation as well. You can feel the warmth of the Sun correct? So when you are in a shadow, you don't feel the sunlight, but when you are in the Sun you can feel the radiation as warmth. Now if the Sun rays are strong enough, and you are not properly protected, you can get a sunburn. This is an effect of radiation or the suns rays.

So you sort of get the idea. Now you have to think a step extra now. While fire is hot and gives of radiation, the radiation is not dangerous to kill us or effect us. Same as the Sun. While it's not healthy to be in the Sun for too long, the effects take time. You can have varying degrees of sunburn. The Earths Atmospher and or the Van Allen radiation belts protect us from the more harmfull radiation the sun gives.

Now you have stuff like Alpha waves, Beta Rays, (not sure what these do, or how bad they are) and the deadly Gamma rays. While they may not be as hot as a fire place or stove, they can be extremly dangerous in a short amount of time.

I hope this sort of helps to explain it simply. Can anyone improve on what I said?

From what I understand radiation does not cause things to become radioactive, which is why radiation treatment in medicine and food treatment is possible. What usually happens is radioactive dust enters the ecosystem, contaminates the soil, is absorbed by plants, which are then eaten by animals and humans.

Please dont' talk about radioactive dust - reminds me of the BBC movie 'Threads'. Gave me nightmares for days.

Yeah, this is correct. I thought it ionizing molecules caused low levels of radiation, but on a small review, I realized that is incorrect.

Not related to radioactive dust, but realted to the BBC - http://www.youtube.com/watch?v=XuKjBIBBAL8

I think I heard a long time ago that alpha and beta waves were even deadlier than gamma rays but when it comes to nuclear detonations they don't stick around very long. I think they both require very close contact to be dangerous.

That is gross. Have a http://www.youtube.com/watch?v=V2Ac6RYSvo8 infestation.

Not all types of radiation are waves in the electromagnetic spectrum.



Alpha and beta radiation aren't waves, they're particles. They aren't necessarily more dangerous but they're all dangerous for different reasons.

Alpha particles are very large, being comprised of a single helium nucleus (two protons and two neutrons) are very ionising and can therefore do a lot more damage before they are absorbed, but since they are so large they hit many atoms as they travel, meaning they disappear quite quickly. Alpha particles can't even pass through your skin and they're stopped after approximately 6 centimetres of air.

Beta particles are much smaller than alpha particles, being comprised of an electron. They aren't as ionising as alpha particles but due to their small size they are very penetrative. They can travel freely through large amounts of air since they won't hit nearly as many atoms in the air (nitrogen, oxygen, etc.) and they can even pass right through your body.

Gamma rays are electromagnetic waves of a very short wavelength. They ionise very weakly but are very penetrative. They can pass right through aluminium and can only be reduced to safe levels if they pass through very thick (like metres) of lead or concrete.

So they're all dangerous. Alpha particles are very ionising and can kill you easily if you get it inside your body (like handling radioactive materials and then accidentally inhaling some dust), beta particles aren't as ionising but they can pass right through you, and gamma particles aren't very ionising at all but they are very difficult to protect yourself from.

Please note, all of these forms of radiation are only dangerous in high levels. In low levels they're very common. They are in the air around us right now and even being made inside our bodies. It is only in high quantities that they are dangerous.

Also sorry if I got anything wrong or used any wrong terminology, this is just what I learned in my physics class.

:yucky: No thanks, you can keep it...

You see, when I want a basic jargon-free explanation of just about anything I go to Simple Wikipedia. Sure it always feels like it's talking down to me, but at least it never assumes I'm a magical nuclear-astro-quantum-helio-mason-vintner-gigalo-scientist wizard.

http://simple.wikipedia.org/wiki/Radiation

To put it simply,radiation is an energy that is being emmited by both natural and man made sources.
Radiation (gamma) is a very high frequency electromagnetic wave.
The difference between harmful gamma rays and the microwaves that your microwave oven produces is the wave's frequency.
Gamma radiation is a wave the same way sun light is a wave.
But sunlight stop at your skin.
Gamma radiation is powerful enough to penetrate your body,so it gets inside you from the front of your body,and gets out from your back!
While this radiation is travelling inside your body,it affects it.
It alters your dna.
Your dna is a complex system of nucleotides (small parts of dna) that all have to be in the perfect line for you to be as you are.
There are hunderds of thousands of nucleotides in a single cubic milimiter of your body,and if only 1 of them isn't at the right place,you have a problem.
Radiation damages your nucleotids.
The damage can vary from amount of radiation taken,and from person to person.
It could be so bad that it can be lethal in just minutes,or cause you cancer,or even get mutated!
But radiation is normal to exist at some low levels.
The normal radiation isn't much enough to risk your health though.

Not quite, your body is very adept at repairing damage to DNA, and the chances of a single damaged nucleotide causing any harm at all is infinitesimally small, you have thousands upon thousands of damaged nucleotides in your body at any one time.
And a mutation is really just any change to your DNA, so all cancers are mutations.

Radiation poisoning isn't caused by damage to your DNA, but to the entire cell.

I think it's 30-50cm of lead or a 2m thick concrete wall that is said to stop gamma rays.

The radiation surrounding us constantly is called background radiation (at least in our physics textbooks ). It's emitted by nearly everything around you.

Well I don't know the exact amount. Our physics textbook says lead only reduces the gamma rays, not stops them, and it says nothing about concrete, I just know that from elsewhere.



That is correct.

Indeed, Beer-Lambert's law says the intensity I after having passed through a material of thickness d is I = I₀e^-μd, where I₀ is the original intensity before passing through the material, and μ is a material and radiation dependent absorpbtion coefficent. For lead with gamma radiation, μ ≈ 0.69 cm^-1, as 1 cm is about enough to reduce the intensity by about 50%.

So, mathematically, you can't completely stop radiation, but in practice you can reduce the intensity to a negligible amount.

To further confuse the OP, the human body contains both Potassium and Carbon both of which can be found to occur naturally in the environment. Both elements are radioactive. The human body also creates gamma rays as the potassium breaks down.

Americanium-241 can also be found in your home. If you have a smoke detector in your house it contains Americanium. It is a radioactive element as well.

And some random number generators use geigher counters.

It should be noted that only particular isotopes of carbon and potassium are radioactive. Carbon 14 is a weak beta emitter, and accounts for <0.001% of the carbon atoms naturally found. Potassium 40 is is also a weak beta emitter (although some of the beta particles can then product gamma radiation when they strike other molecules), and accounts for ~0.01% of naturally found potassium atoms.