Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Medical Is microwave cooking safe?

  1. Oct 29, 2009 #1
    Hi everyone:

    Have you ever heard anything about the effects of the microwave on body?

    ..
     
  2. jcsd
  3. Oct 29, 2009 #2

    Pythagorean

    User Avatar
    Gold Member

    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.
     
  4. Oct 29, 2009 #3

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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?
     
  5. Oct 29, 2009 #4
    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?


    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?
     
  6. Oct 29, 2009 #5

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Of course they don't, because microwave ovens do not emit *any* ionizing radiation.
     
  7. Oct 29, 2009 #6
    wait a minute, as far as I know, these ovens are working with high frequency waves. at those frequencies, if you stand near them, they will penetrate to your body and damage your tissues. but they damp in the air, so standing far away form them can reduce this damage. in ovens, they shield the device, that means it will absorb the waves and keeps them inside. 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?
     
  8. Oct 29, 2009 #7

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    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.

    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.
     
  9. Oct 29, 2009 #8

    Pythagorean

    User Avatar
    Gold Member

    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.

    BUT, frustrated total internal reflection happens when you get your face close to the microwave. The waves will transmit through the 2nd medium (the air) to the third medium (your face) because the distance between your face and the microwave is on the order of microwaves (meters to millimeters). I don't know if enough power actually makes it through to be concerned about, but I don't NEED to put my face there, so I won't test it, personally.
     
  10. Oct 29, 2009 #9
    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 [Broken]
     
    Last edited by a moderator: May 4, 2017
  11. Oct 29, 2009 #10

    Pythagorean

    User Avatar
    Gold Member

    Last edited by a moderator: May 4, 2017
  12. Oct 29, 2009 #11

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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
     
  13. Oct 29, 2009 #12
    D H and others:
    Thank you for your time. Helpful answers.
    This is applied to me. I am electrical eng. )

    exactly!

    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.

    The problem is with the high power at this frequency, I assume.

    But my question is about the FOOD which is cooked with microwave oven.

    Do you know what happens to them?
     
  14. Oct 29, 2009 #13
    Thank you chroot and Pythagorean:

    So, can we have evanescence waves (as Pythagorean mentioned)inside a metallic cavity? I mean there's no loss inside the cavity and if we assume that the cavity is designed for the operating frequency of the power generator (like a resonating cage), there should be a standing wave. Right?
     
  15. Oct 29, 2009 #14

    Pythagorean

    User Avatar
    Gold Member

    So FTIR doesn't apply to conducting surfaces (remembering that they're not perfect conductors so there's some penetration depth)? It was my optics professor who brought up the concern, but he's a physicist, not an engineer.

    You're right though, I've never seen a microwave without the mesh on the glass; I should have considered that.
     
  16. Oct 29, 2009 #15

    Pythagorean

    User Avatar
    Gold Member

    also, I do have a microwave meter, and i DO pickup over 1mw/cm^2 (the needle tops out) into the front of the meter. But I haven't measured area of the front of the box. It's roughly 4x6 cm^2. This has been true for all three of the microwaves (~10 year old models) that I've measured it on.

    I don't know if that's significant with regards to biology. The device I used was the TriField Meter: http://www.trifield.com/EMF_meter.htm

    Also, I don't trust manufacturer claims, as I've been taught not to in my engineering courses (especially considering the economics of LEDs), so this:

    isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.
     
    Last edited: Oct 29, 2009
  17. Oct 29, 2009 #16

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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.
     
  18. Oct 29, 2009 #17
    Thank you. I somehow got the answer.
     
  19. Oct 29, 2009 #18

    russ_watters

    User Avatar

    Staff: Mentor

    Though I'm not sure of the mechanism for enforcement, they are required to be tested to meet government standards on leakage:
    http://www.hps.org/hpspublications/articles/microwaveoven.html
     
  20. Oct 29, 2009 #19

    russ_watters

    User Avatar

    Staff: Mentor

    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
     
  21. Oct 29, 2009 #20

    Pythagorean

    User Avatar
    Gold Member

    What kind of materials can store radiation, and then release it as radiation anyway?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Is microwave cooking safe?
  1. Microwave and cancer? (Replies: 43)

  2. Microwave food (Replies: 12)

  3. Bacteria and Microwave (Replies: 19)

  4. Cooked/raw food (Replies: 1)

Loading...