what is radiation

[dragonstar57]

when we say radiation what do we really mean?

are we talking about an electromagnetic wave?

alpha/beta particles?

radionuclides?

is radiation that we would be exposed to the same as what would be released by a fission reactor? (weather a 3 mile island situation or a Chernobyl like situation) as the background radiation from other sources?

and can someone explain the units that they use when talking about radiation and why if they are EM they are not measured in mW or something similar?

Edited March 17, 2011 by dragonstar57

[Klaynos]

All of the above.

 

And the units depends on context and what you are counting.

 

If you are talking about radiation from nuclear reactions then we normally use counts, so the number of events, but you can also talk about energies, whether this is an energy/particle or a flux will again depend on context.

[swansont]

Radiation is any energetic particle released in a nuclear reaction. Alphas, betas, gammas, neutrons, protons, neutrinos.

[dragonstar57]

Radiation is any energetic particle released in a nuclear reaction. Alphas, betas, gammas, neutrons, protons, neutrinos.

so is there a difference between the BG radiation from the sun space etc

and what would be released in a nuclear accident?

and how does that definition differ from the definition i was taught "radiation is any energy that radiates" (or can move through a vacuum)

this definition seems to imply a strict understanding of radiation as an energy wave but I suppose it isn't that simple (is this dealing with quantum mechanics?)

Edited March 17, 2011 by dragonstar57

[lemur]

Radiation is any energetic particle released in a nuclear reaction. Alphas, betas, gammas, neutrons, protons, neutrinos.

How can you call a photon from the sun "radiation," and then say the same photon is not "radiation," once it is absorbed and re-emitted by an atom? To me the word, "radiation" just refers to anything "radiating," and "radiate" refers to anything moving linearly away from a source. Thus, I would think it would refer to all EM waves/photons, plus neutrons and other particles that radiate away from their source. If that definition is too broad, how can you justify differentiating between two photons of the same wavelength just based on their circumstances of emission? As particles/energy in themselves, they are indistinguishable from each other, no?

[swansont]

How can you call a photon from the sun "radiation," and then say the same photon is not "radiation," once it is absorbed and re-emitted by an atom?

 

Um, because I didn't say that?

 

 

To me the word, "radiation" just refers to anything "radiating," and "radiate" refers to anything moving linearly away from a source. Thus, I would think it would refer to all EM waves/photons, plus neutrons and other particles that radiate away from their source. If that definition is too broad, how can you justify differentiating between two photons of the same wavelength just based on their circumstances of emission? As particles/energy in themselves, they are indistinguishable from each other, no?

 

The context of the OP was nuclear accidents. The point is that ANY particle emitted is radiation.

 

so is there a difference between the BG radiation from the sun space etc

and what would be released in a nuclear accident?

and how does that definition differ from the definition i was taught "radiation is any energy that radiates" (or can move through a vacuum)

this definition seems to imply a strict understanding of radiation as an energy wave but I suppose it isn't that simple (is this dealing with quantum mechanics?)

 

Nothing fundamental, i.e. your body can't tell the difference. The distinction is in the energy spectrum and the intensity. Non-ionizing radiation isn't much of an issue, and BG levels are generally low. "Any energy that radiates" is OK, though the radiation is the particle; energy isn't an entity.

 

The big problem in a nuclear power incident, as Ydoaps pointed out in another thread, is the spread of contamination, i.e. radioactive particles, rather than the radiation from the reactor itself. If it were just the radiation, you simply wouldn't go near it and/or you'd put up a wall to attenuate the radiation. Radioactive sources that you ingest or inhale are potentially much more damaging than external sources, if they are alpha- or beta-emitters, so the spread of those is the big concern.

[lemur]

The context of the OP was nuclear accidents. The point is that ANY particle emitted is radiation.

I realized the context of the post was regarding nuclear accidents, but I find it confusing to many lay people to think of radioactivity as fundamentally different from, say, particulate glowing coal dust. Basically, I tend to think of radioactive material as hot coals that don't require oxygen or any other external inputs to generate heat. Still, I realize this analogy doesn't address the effects of non-EM particles such as neutrons.

 

Nothing fundamental, i.e. your body can't tell the difference. The distinction is in the energy spectrum and the intensity. Non-ionizing radiation isn't much of an issue, and BG levels are generally low. "Any energy that radiates" is OK, though the radiation is the particle; energy isn't an entity.

Right, I think I used to think that there was something inherently poisonous about radioactive material that had nothing to do with the heat/light generated. I think neutrons and higher frequency EM waves (UV, X-ray, and gamma-rays) can damage cellular DNA because they penetrate flesh, but I think this would be somewhat like having open-heart surgery in the sunlight. Your inner flesh would probably get sunburned much quicker than your outer skin, but it would still take a couple minutes, I think, and at low levels, radiation tends to have beneficial effects, I think, like exposing an infected wound to sunlight.

 

The big problem in a nuclear power incident, as Ydoaps pointed out in another thread, is the spread of contamination, i.e. radioactive particles, rather than the radiation from the reactor itself. If it were just the radiation, you simply wouldn't go near it and/or you'd put up a wall to attenuate the radiation. Radioactive sources that you ingest or inhale are potentially much more damaging than external sources, if they are alpha- or beta-emitters, so the spread of those is the big concern.

But shouldn't someone calculate the concentration of the particles in their air if its getting exhausted as vapor? If ppm levels drop to low enough levels, doesn't the long half-life of the particle practically guarantee it won't split while in your system, and even if it did, would it cause that much damage acting in isolation? I think like any other kind of exposure, it is relatively intense exposure over prolonged periods that raises risk. Isolated exposures to relatively low-concentrations can't have very significant effects with radioactive material any more than chemicals, can they? I would guess that many people who would be in panic if they were near the Japanese reactor right now have no problem using relatively strong chemicals (such as oven-cleaners) or eating food prepared using equipment cleaned with them.

 

I've actually read that prior to WWII, radiation therapy was widely used and even sold over the counter as "liquid sunshine" to be ingested as a general cure-all and elixir. The main problems of radiation were suffered by doctors and technicians who were subject to constant exposures. The book I read on this even showed that cancer rates are actually lower in areas with slightly higher levels of background radiation and among workers who built nuclear weaponry. There was also a table of longevity vs. life expectancy in the areas where the nuclear bombs were dropped in WWII, and it showed that while there were shorter average lifespans for people according to distance from the blast-center, there is a point just before "average longevity" where people actually lived longer on average due to radiation exposure. Of course, this is little consolation to anyone whose life was shortened by exposure, but it is striking that some lives were actually prolonged (according to this book I read anyway - it was titled "the Good News about Radiation" btw).

 

Misinformation about radiation tends to inspire fear in people. I can remember a debate some years ago whether bananas should be irradiated to preserve freshness and people were afraid of eating irradiated bananas, as if they would become radioactive from being exposed to UV lamps or whatever they were doing to them. What's worse about this, imo, is that once people accept food-radiation as safe, though, they no longer care that it sterilizes the seeds so they can't be used by farmers, for example. That's a topic for another thread, though, I know.

 

 

Edited March 17, 2011 by lemur

[swansont]

I realized the context of the post was regarding nuclear accidents, but I find it confusing to many lay people to think of radioactivity as fundamentally different from, say, particulate glowing coal dust. Basically, I tend to think of radioactive material as hot coals that don't require oxygen or any other external inputs to generate heat. Still, I realize this analogy doesn't address the effects of non-EM particles such as neutrons.

 

Part of the problem is people thinking of radioactive things as glowing green. Another is not distinguishing between ionizing and non-ionizing radiation, which is why fear-mongers are successful in getting people to be afraid of power lines and cell phones.

 

But shouldn't someone calculate the concentration of the particles in their air if its getting exhausted as vapor? If ppm levels drop to low enough levels, doesn't the long half-life of the particle practically guarantee it won't split while in your system, and even if it did, would it cause that much damage acting in isolation? I think like any other kind of exposure, it is relatively intense exposure over prolonged periods that raises risk. Isolated exposures to relatively low-concentrations can't have very significant effects with radioactive material any more than chemicals, can they? I would guess that many people who would be in panic if they were near the Japanese reactor right now have no problem using relatively strong chemicals (such as oven-cleaners) or eating food prepared using equipment cleaned with them.

 

Right. Chronic moderate exposure is generally more dangerous, unless the acute exposure is a really large dose. Your body gets damaged and then repairs itself. As long as the damage is not severe, you can recover. The problem with ingesting/inhaling the contaminants is that there are materials that stay in your body a long time, and the decay lifetimes aren't necessarily that long compared to the number of atoms. The activity (# of decays per unit time) depends on both the half-life and the number of atoms.

 

I've actually read that prior to WWII, radiation therapy was widely used and even sold over the counter as "liquid sunshine" to be ingested as a general cure-all and elixir. The main problems of radiation were suffered by doctors and technicians who were subject to constant exposures. The book I read on this even showed that cancer rates are actually lower in areas with slightly higher levels of background radiation and among workers who built nuclear weaponry. There was also a table of longevity vs. life expectancy in the areas where the nuclear bombs were dropped in WWII, and it showed that while there were shorter average lifespans for people according to distance from the blast-center, there is a point just before "average longevity" where people actually lived longer on average due to radiation exposure. Of course, this is little consolation to anyone whose life was shortened by exposure, but it is striking that some lives were actually prolonged (according to this book I read anyway - it was titled "the Good News about Radiation" btw).

 

It's called hormesis. I don't know how much of it is legitimate and how much is not; there are certainly illegitimate applications of the concept (e.g. homeopathy)

 

Misinformation about radiation tends to inspire fear in people. I can remember a debate some years ago whether bananas should be irradiated to preserve freshness and people were afraid of eating irradiated bananas, as if they would become radioactive from being exposed to UV lamps or whatever they were doing to them. What's worse about this, imo, is that once people accept food-radiation as safe, though, they no longer care that it sterilizes the seeds so they can't be used by farmers, for example. That's a topic for another thread, though, I know.

 

Ironic, as bananas are one of the more radioactive foods to begin with.

[lemur]

Part of the problem is people thinking of radioactive things as glowing green. Another is not distinguishing between ionizing and non-ionizing radiation, which is why fear-mongers are successful in getting people to be afraid of power lines and cell phones.

I always figured that uranium or some other radioactive element did actually have a green glow and that was where the stereotype emerged. Cell phones and microwaves don't concern me much. I do wonder about magnetic fields though since I would think they would cause the iron in your body to (attempt) to re-arrange according to the direction of the field. I can't imagine this would pose a problem except maybe if you spent a lot of time in the same house or office with the same field strength and direction on you all the time. If that happened, I would expect some patterns of iron build-up in your blood to occur or something. Idk, it's admittedly very speculative based on a vague sense that magnets affect iron dust.

 

It's called hormesis. I don't know how much of it is legitimate and how much is not; there are certainly illegitimate applications of the concept (e.g. homeopathy)

When I read about radium-drinks being sold as "liquid sunshine," it made sense to me that exposing your digestive tracts to "sunshine" could have a positive (anti-biotic) effect, the way that it can be good to expose infected flesh to sunlight. I suppose what you keep saying about the ionizing vs. non-ionizing is that some radioactive material can ionize and thus bond within your cells instead of flushing through your system, in which case you'd have to deal with longer-term exposure.

[swansont]

I do wonder about magnetic fields though since I would think they would cause the iron in your body to (attempt) to re-arrange according to the direction of the field.

 

Not so much. Iron in hemoglobin is not ferromagnetic. (It is weakly paramagnetic). Getting an MRI would not end well if the iron interacted that strongly with the magnets. (For iron possibly in tattoo ink or otherwise not bound up in your blood, all bets are off.)

[dragonstar57]

is the spread of contamination, i.e. radioactive particles, rather than the radiation from the reactor itself. If it were just the radiation, you simply wouldn't go near it and/or you'd put up a wall to attenuate the radiation. Radioactive sources that you ingest or inhale are potentially much more damaging than external sources, if they are alpha- or beta-emitters, so the spread of those is the big concern.

so it's like siting under a light vs. eating a light bulb (in the sense that the source is inside the body rather than outside)?

 

what is neutron radiation?

what is ionizing radiation?(as i understand it takes electrons away from stable atoms and that messes with bio-molecules)

why alpha/beta are they called radiation as far as i know a beta particle is a high speed positron or electron and alpha is a high helium nucleus

also just wondering is this thread in terms of Quantum mechanics,

i keep hearing about EM being particles and that is a little confusing.

[swansont]

so it's like siting under a light vs. eating a light bulb (in the sense that the source is inside the body rather than outside)?

 

Sorta, yes. Your skin (especially the dead cells on the outer layer) provides a certain measure of protection against charged particle radiation.

 

 

what is neutron radiation?

what is ionizing radiation?(as i understand it takes electrons away from stable atoms and that messes with bio-molecules)

why alpha/beta are they called radiation as far as i know a beta particle is a high speed positron or electron and alpha is a high helium nucleus

also just wondering is this thread in terms of Quantum mechanics,

i keep hearing about EM being particles and that is a little confusing.

 

Neutron radiation is neutrons. They scatter and ionize atoms, and can be absorbed and turn a nucleus into a radioactive isotope. Anything that ionizes atoms is potentially a problem, because ions interact differently than neutral atoms and this can disrupt the body's chemical interactions. You damage DNA.

 

EM radiation is called photons; it interacts like a particle, causing ionization. Alphas and betas are as you describe, and are emitted in certain decays.

[zapatos]

so it's like siting under a light vs. eating a light bulb (in the sense that the source is inside the body rather than outside)?

And to swansont's point, you can walk away from the light bulb you are sitting under, and you will no longer be exposed to its radiation. Since you cannot walk away from the light bulb you swallowed you continue to be exposed to its radiation.

Edited March 18, 2011 by zapatos

[dragonstar57]

what happens when a ion is hit by ionizing radiation?

could it "de-ionize" it?

[Girish Kumar]

Well its good question.

 

As a person who is working in the same field, I do describe Radiation as a flux of energetic particles or rays which do have origin from atomic or nuclear transitions. And an interesting fact is that we are always in exposure of radiation. As I have told, the energetic particles emanating from outside universe would be reaching the surface of the earth but losing intensity by greater margin. The intensity of these radiations would be different in different regions due to magnetic belts of earth. Such radiation we usually call as cosmic or terrestrial radiation and commonly used word background radiation. The sunlight radiation contains UV, infrared also which are also called as solar radiation.

 

The units of radiation are classified into 3 types. One is for estimating the exposure rate and the unit is R/hr (Roentgen/hour).

It gives the amount of charge liberated in 1 cubic centimeter of air.

Second is RAD(Radiation Absorbed Dose), which describes the amount of energy deposited in unit mass of a substance.

Third is REM(Roentgen Equivalent Man) which is used for estimating biological effectiveness on living beings.

 

I have answered you question briefly for your understanding.

 

You can visit my blog http://physicsdatabank.blogspot.com for more answers on conceptual questions.