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Si14
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Hi everyone:
Have you ever heard anything about the effects of the microwave on body?
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Have you ever heard anything about the effects of the microwave on body?
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Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.
Si14 said:Hi everyone:
Have you ever heard anything about the effects of the microwave on body?
..
Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?Pythagorean said:I don't know about the food; I trust it in general, but I can tell you something about frustrated total internal reflection:
When teaching us about frustrated total internal refraction, my optics teacher stated that he never got his face close to the microwave to check his food while it was running anymore.
Thank you. Of course they have some standards for radiation dosage emitted from microwave ovens. And they can test them simply by measuring the radiation and power around and far away from ovens, BUT, how about the food which is prepared by this method? I think I read some where that some Russian groups are working on the effects of microwave cooked foods on body? Have you heard about that?Moonbear said:Yeah, it's bad to microwave your body. Did you have a more specific question? Are you asking about eating the foods cooked in a microwave, or the shielding on microwave ovens, or something else entirely?
Of course they don't, because microwave ovens do not emit *any* ionizing radiation.Si14 said:Of course they have some standards for radiation dosage emitted from microwave ovens.
D H said:Of course they don't, because microwave ovens do not emit *any* ionizing radiation.
Your use of words such as "high frequency waves" and "radiation dose" makes me think that you are thinking of things like x-rays and gammas given off by radioactive elements such as uranium, radium, etc. That is not what goes on in a microwave oven. The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house. It is a very low frequency compared to the radiation you are familiar with. It is an extremely low frequency compared to the damaging ionizing radiation associated with radioactive elements. The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.Si14 said:wait a minute, as far as I know, these ovens are working with high frequency waves. ... so it minimizes the radiation dose outside the shield. But what is Ionizing radiation? you mean after bombarding the food by these waves, they will be ionized (for example hydrogen or carbon) and will radiate also?
Si14 said:Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?
Am I correct?
D H said:The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.
waht said:Yes that's true. Microwaves are not ionizing - the standard designation does not reflect the whole electromagnetic spectrum.
http://img405.imageshack.us/img405/6813/rfband2.jpg
Pythagorean said:I was referring to when you get your face close to an operating microwave. There's a glass wall between you and the microwaves, so we normally assume total internal reflection: that is, the microwaves are bouncing around inside the microwave, and staying inside there.
This is applied to me. I am electrical eng. )D H said:The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.
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exactly!D H said:The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house.
That's what I meant. and I think that they can make good shields for that. Since it looks simple, for shielding each frequency (at microwave ovens, I think they are around 2.5GHz), a good absorber needs to be fabricated.D H said:The problem with microwaves isn't that they are radioactive. The problem is that the very feature that makes microwaves able to cook foods placed inside the oven makes microwaves able to heat things up outside the oven if the oven is not properly shielded.
chroot said:The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.
chroot said:I believe you are spreading misinformation. Your thoughts on FTIR are accurate, but you are applying the concept indiscriminately. The glass is wholly irrelevant to the propagation of the microwaves, or the safety of the people who use the oven.
The microwave door includes a fine mesh of metal, behind the glass. The holes in the mesh are large enough for you to be able to see your food (high-frequency visible photons pass right through the holes), but too small for the low-frequency microwave photons to escape. The microwaves have wavelengths on the order of 12 centimeters, and the holes are much, much smaller. The mesh is essentially a solid piece of metal, as far as the 12 cm radiation is concerned. The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.
You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.
Your microwave oven is not unsafe, even if you put your face near it. Relax.
- Warren
You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.
Si14 said:But my question is about the FOOD which is cooked with microwave oven.
Do you know what happens to them?
Moonbear said:It gets cooked. It's fine to eat, if that's your question. Once the microwave oven is turned off, there is no more emission of the microwaves. It's not like a radioactive isotope that would contaminate something and linger.
The only potential issue is whether some foods are exposed to the microwaves long enough to kill bacteria with such a short cooking time.
Though I'm not sure of the mechanism for enforcement, they are required to be tested to meet government standards on leakage:Pythagorean said:...isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.
http://www.hps.org/hpspublications/articles/microwaveoven.htmlAll new microwave ovens produced for sale in the United States must meet the Food and Drug Administration/Center for Devices and Radiological Health (FDA/CDRH) performance requirements in Title 21, CFR, Part 1030.10. This requirement states that new ovens may not leak microwave radiation in excess of 1 mW cm–2 at 5 cm from the oven surface. It also states that ovens, once placed into service, may not leak microwave radiation in excess of 5 mW cm–2 at 5 cm from the oven surface. The "Procedure for Field Testing Microwave Ovens" (HEW Publication (FDA) 77-8037) is the standard method for verifying that these oven performance criteria are met.
Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.Moonbear said:It's not like a radioactive isotope that would contaminate something and linger.
russ_watters said:Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.
http://en.wikipedia.org/wiki/Food_irradiation
Pythagorean said:What kind of materials can store radiation, and then release it as radiation anyway?
chroot said:Depending upon what you mean by "radiation," the answer might be any material. If you bombard just about anything with protons or neutrons, it'll end up radioactive.
- Warren
russ_watters said:Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.
http://en.wikipedia.org/wiki/Food_irradiation
Pythagorean said:I suppose I was referring to electromagnetic radiation, specifically microwaves in this case. Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?
Any material above absolute zero should manage to do thatPythagorean said:Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?
=D H;2432070]
The heat of your oven or range is not all that great for living tissue, either.
One of the key reasons we cook food is precisely because heat is not all that great for living tissue. That heat kills all of (or at least most of) those nasty microbes that grow on our food.
Moonbear in post #16 did raise one issue regarding microwave ovens: The short cooking time might not be hostile enough to living tissue.
Microwave radiation is only radiation in the electro-magnetic sense, your regular stove uses infrared radiation, a light bulb uses visible radiationJasongreat said:but when it comes to radiation I am very conservative, I try not to eat irradiated foods either.
It also breaks down tissue to make it easier to eat - it's a lot easier to eat chicken casserole than raw chicken.but do we use heat because it is the best/only way or is it just the the easiest way?
Sometimes the bacteria are in the source however clean the processing. Milk inside the cow can contain dangerous bacteria. You can get a variety of diseases straight form the teat, just as you could 100 years ago.When governments started to mandate cooking milk to kill the microbes it was far easier and less expensive than making the dairies clean up,...impossible to order a hamburger less than well done, we can get away with a far dirtier food supply
It's the energy that the microbes absorbs - which is a combination of heat and time. The danger of a microwave is that the food might not have time to heat up fully all the way through and so the centre might not get hot enough for long enough to kill the microbe.Isnt it the heat value that kills microbes and not the length of time? On cooking
mgb_phys;2432361]Microwave radiation is only radiation in the electro-magnetic sense, your regular stove uses infrared radiation, a light bulb uses visible radiation
It also breaks down tissue to make it easier to eat - it's a lot easier to eat chicken casserole than raw chicken.
Sometimes the bacteria are in the source however clean the processing. Milk inside the cow can contain dangerous bacteria. You can get a variety of diseases straight form the teat, just as you could 100 years ago.
Pasteurizing is a cheap and easy way of partially cleaning milk - at least enough for it to be safe for two weeks. If you want it to last longer you can heat it more to kill more bacteria but you destroy more milk proteins and end up with nasty sterilized milk.
It's the energy that the microbes absorbs - which is a combination of heat and time. The danger of a microwave is that the food might not have time to heat up fully all the way through and so the centre might not get hot enough for long enough to kill the microbe.
Electromagnetic radiation is dangerous, but due to it's heating effect (at > visible wavelengths) if you stand in front of a powerful enough microwave transmitter for long enough you will be damaged. It's unlikely that a 1W cell phone outside your head could do much heating.Jasongreat said:Ibut lately there seems to be lots of studies showing or atleast claiming the dangers of electro-magnetic radiation
You eat raw fish! The danger with chicken is that they are generally raised in less than sanitary conditions so the disease risk is rather high.The example you give about made me toss my cookies, raw chicken, although I did see a show on the travel channel where there is a place in japan where they eat raw chicken,
True but there is still a chance of mastitus/bovine TB/ etc. There is probably less risk in hand reared hand milked cows simply because the farmer would notice any illness and there is less chance of transferring contamination through milking machines.The cleaner you keep the dairy the less chance of bacteria in the milk,
Probably too low a temperature to destroy milk protein.Your last sentence above makes me ask if the original cooking(pasteurization) doesn't destroy some proteins, enzymes and such as well as the bacteria?
Not sure, lactose does depend on the amount of fat so there might be a differnet reaction to full fat milk than 2% supermarket milk.According to the raw milk supporters lactose intollerant people can drink raw milk since it still has the enzymes to allow them to make use of the lactose where pasteurized milk has those enzymes destroyed.
Common urban myth. In fact because of the short cooking time and poor thermal conductivity you can end up with the inside much less cooked than in a stove.I thought that microwaves cooked from the inside out
True of steak, not true of hamburger - once you mince it you mix 'surface' all through the meat.since all/most bacteria is on the surface unless it has been ground and mixed we could still be in danger.
Yes.Jasongreat said:What is the purpose of the shield in a microwave? Isnt it to keep the dangerous microwaves inside the oven?
Yes, the reason microwaves are bad for us is because we are alive: it is dangerous to cook a person while they are alive!Since microwaves are not good for organic material outside the oven wouldn't it be not good to the organic material inside? Granted the organic matter outside is alive and the organic matter inside is dead and that could be the reason microwaves are dangerous to us but not to the food we are cooking, but I am not so sure.
Your microwave has a shield to prevent microwaves from escaping and cooking you. Similarly, your normal oven has a shield to keep heat (hot air) from escaping and cooking you.Agreed, however I haven't noticed a shield around my conventional oven to keep the microwave radiation in.
=mgb_phys;2432549]Electromagnetic radiation is dangerous, but due to it's heating effect (at > visible wavelengths) if you stand in front of a powerful enough microwave transmitter for long enough you will be damaged. It's unlikely that a 1W cell phone outside your head could do much heating.
The point remains that we cook food both for texture/taste and safety.
Probably too low a temperature to destroy milk protein.
Common urban myth. In fact because of the short cooking time and poor thermal conductivity you can end up with the inside much less cooked than in a stove.
russ_watters;2432616] Yes, the reason microwaves are bad for us is because we are alive: it is dangerous to cook a person while they are alive!
.Your microwave has a shield to prevent microwaves from escaping and cooking you. Similarly, your normal oven has a shield to keep heat (hot air) from escaping and cooking you