What is Microwaves: Definition and 79 Discussions

Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm). In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave technology. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
Microwaves travel by line-of-sight; unlike lower frequency radio waves they do not diffract around hills, follow the earth's surface as ground waves, or reflect from the ionosphere, so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band, they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer. Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openers and keyless entry systems, and for cooking food in microwave ovens.

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  1. L

    I How to calculate the ring resonator radii via Laplace?

    Dear forum, I was trying out two different approaches to calculate the dimensions of a ring resonator (sketch below) and got two slightly different solutions. The first approach is to assume that the waveguide wavelength has to fit n times onto the circumference of the ring (taking the average...
  2. heroslayer99

    Path difference of microwaves

    I understand the equation (path difference)/wavelength x 2pi = phase difference, but in this case I do not know how changing the distance of H from the source will affect the path difference. In addition to this, does minima refer to 0 amplitude (complete destructive interference) or does minima...
  3. S

    Finding frequency of microwaves

    I thought 14 mm, 86 mm, 156 mm, 225 mm and 293 mm are the position where constructive interference happens 14 mm is the position of 1st maxima, 86 mm is the position of 2nd maxima and etc (measured from a certain position of center maxima) But when I used that numbers to calculate the fringe...
  4. A

    Active burn control by using microwaves to control the detonation of the engine

    I was thinking the other day, would it be possible to have microwaves heat the air fuel mixture to activation point and have the microwaves bounce back off the gas to be picked up by a computer that generates a 3d image. this 3d image could be used to heat the gas up in a uniform way so as to...
  5. A

    MHB Probability of cancer because of microwaves

    Please help understand how to solve this question. Sorry for the terrible English. If there’s 10% chance of getting cancer from microwaves, and 3% of the population gets cancer, what is the probability that a certain person who have cancer and was exposed to microwaves got it as a result from...
  6. P

    Discover How to Efficiently Polarize Microwave Radiation | 1mm Wavelength

    Ok, here is the scenario, kinda weird but please entertain me. Say I had a huge amount of microwave radiation being shot in a particular direction. Let's say they have a wavelength of 1mm. How would i go about polarizing the microwave radiation?
  7. T

    How Do Microwave transmitters work without physical connections?

    So I recently picked up 40 of 10.525 GHz Microwave RADAR transmitters: I opened up one out of curiosity and had something like this (image attached) . I noticed some parts of the PCB aren't even connected to anything. How do the different shapes and sizes of the PCB interact with each-other...
  8. E

    Different metals and their compounds' reaction to Microwaves

    Does anyone know of any studies into exactly how much various metals reflect or absorb microwaves with relationship to the microwaves wavelength and ideally theyt compounds too?
  9. J

    Microwave Interference and Signal Detection: Understanding Homework Question

    Homework Statement I have attached the question to this thread as it requires looking at a diagram. Homework Equations None The Attempt at a Solution We are supposed to attempt the question and mark it but I have a few questions if people could kindly answer for me please. In the main 6 mark...
  10. M

    Loop Antennas vs. B-Probes: Similarities and Differences

    Hi the difference between a loop antenna and a magnetic probe (B-Probe) is only that the loop antenna works in far field and B-Probe works in near field? The standard features of magnetic antenna (antenna factor, impedance matching, radiation patterns, efficiency, ecc) have the same definition...
  11. R

    Are microwave susceptors attenuated in viscoelastic mediums?

    Are microwave susceptors attenuated in viscoelastic mediums ? I am experimenting with some widely known microwave susceptors like iron oxide and silicon carbide (materials that normally convert RF to heat quite effectively). In ceramic formulations they perform great, as expected. When...
  12. S

    How to focus and direct microwaves?

    I am interested in building a microwave powered toy helicopter purely for the fun of it. As we have discovered in our initial research, it isn't possible to direct the microwaves from a microwave oven magnetron too far. I know that those microwaves are of a similar wavelength (or is it?) What...
  13. N

    B Can we know what exists in planets' subsurfaces?

    imagine this situation: there's a very similar planet to Earth with almost the same atmosphere and surface. we want to know what lies beyond the surface to know if life exists there. so could we send or observe radio waves or microwaves with a similar telescope as arecibo that penetrates several...
  14. N

    Can microwaves either change the eV of electrons, or move....

    -the electrons to the same shell levels of glass as the microwaves pass through and heat the material, or move electrons in a opaque material to the same energy levels, or shell levels of glass, and transparent liquids, and some plastics. In a microwave the waves traverse food, and heat the food...
  15. I

    Sonoluminescence using microwaves?

    Would it be possible to produce the same effect using electromagnetic waves instead of sound waves?
  16. Invutil

    Why is visible light not harmful?

    [unacceptable source deleted] Microwaves have a wavelength greater than visible light and are harmful. Ultraviolet light has wavelengths smaller than visible light and is harmful. In what ways are the two harmful and why isn't visible light harmful in the same ways? I'm a total noob. Just...
  17. vinusherkhane

    When we can say that a waveguide is perfectly matched?

    please explain somebody what it means I am totally confused.
  18. 3

    Investigation into the behavior of microwaves

    Hi, For an assignment at school I am looking into the behaviors of microwave propagation. For instance I have familiarized myself with Fraunhoffer diffraction (Single slit, Double slit and grating) and an amount of wave mechanics in general. What I would like to do however is to link all...
  19. M

    Dielectric resonator - microwaves

    Hi, recently there was an article in one scientific journal where they claimed that when microwaves are shined on a mixture of dielectric solid (powdered or crystalline) of high dielectric constant with some liquid, the EM field is much higher, both in the dielectric and in the liquid, as...
  20. X

    Is it possible to partially reflect microwaves as we can do with light?

    Different types of mirrors and reflective surfaces can be set up to reflect predetermined amounts of light, like 70% of it, or 30%, or 99% of it, while letting the rest through. Can the same be done with microwaves? It seems even very very weak metal cages can completely reflect microwaves. Is...
  21. G

    Why do we observe only microwaves in the background radiation?

    Why aren't the other bands (visible, UV, etc.) in the electromagnetic spectrum also seen today as part of the background radiation?
  22. S

    Microwaves and Interference problem

    I'm working on my physics prelab, but I can't seem to get this answer. The question states: Measuring the detector´s output as a function of its position along the goniometer (look it up!), we see that there are maxima and minima in the signal. Starting at one of the maxima, we find 6...
  23. T

    Can Microwaves Fuse Metal Particles on a Plastic Substrate?

    Greetings! I'm interested in depositing a Line of fine copper powder on a plastic substrate. Due to Limitations of my situation, I want to explore the possibility of using tuned microwaves to fuse the copper particles to form a continuous conductive path. I'm aware microwaves bounce off...
  24. V

    Can I Use Microwaves to Study Asteroids?

    How would I shoot microwaves at a piece of asteroid? Scientist shot something which I forgot, And they could get data from it? Is that possible for a price of 2,000$ I would love to see if I could find out compositions of asteroids. And what could I use? I know that NASA probably uses morse...
  25. C

    Absorption coefficient of aluminium for microwaves

    I am looking for an exact value of absorption coefficient of aluminium for microwaves, but I can not find it in the internet. Anyone knows where I can find it?
  26. O

    Can Bicycles Generate Enough Power to Run Microwaves?

    My friends and I have thought about this for a few years now and still can't come to a conclusion. If an electronic device was placed on a push bike and could be powered by it (for arguments sake we came up with a microwave) and was turned on while in motion, would the bike become harder to...
  27. S

    What Career Opportunities Exist in RF Circuits and Microwaves Field?

    My school offers a concentration in RF Circuits and Microwaves in their EE program. I have an idea about what some potential jobs/careers that use these topics are but am not sure. Can anyone tell me more about the concentration are/field and what jobs would be available in it or what some...
  28. D

    Microwaves through an ice sphere: Which scattering solution is best?

    I apologize for not following the template, but it doesn't really fit. I would have posted it elsewhere but as it's for academic purposes I think it has to be here. Please excuse me if I'm wrong. I'm a high schooler working on a project, and I was planning to send ≈3 cm microwaves through an...
  29. E

    Why are microwaves reflected by the door?

    Hi, I am wondering why microwaves don't escape through the door? The most common answer seems to be that the wavelength of microwave ovens is about 10-15cm which is much larger than the 1-2mm holes in the grille. But isn't the wavelength of light really just within a vector space of...
  30. Roodles01

    What is the relationship between frequency and cross section in a waveguide?

    I have a question relating to waveguides. Fine, but having looked at what TE TM modes are I don't really see how I can find the frequency of the μwave with the information I have.Homework Equations A waveguide with dimensions a & b (short & long sides respetively) propogates in the TM10 mode...
  31. I_am_learning

    Microwaves and Electro-magnetic waves (lame questions)

    Microwaves are said to be Electromagnetic waves with frequency 300 Mhz to 300 Ghz. If so, then, is the CPU of my computer running at 2Ghz, emitting some sort of microwave ? Is the microwave cooking tiny drops of water around ? (I say so, because, if the CPU is running at 2GHz, currents must be...
  32. E

    Electromagnetic fields and microwaves

    I need some help with properties of electromagnetic fields in the presence of microwaves. specifically will a electromagnets field, powered by an external power supply, function normally in a microwave chamber? Will the magnetron induce a current in the copper coil? Would the external power...
  33. E

    Heating with Microwaves: An Efficient Way to Warm Your Home?

    Could it be possible to heat the people in a house with long wavelength microwaves rather than heating all the air in the building ?
  34. K

    Medical Which frequencies does an MRI machine use? Is it microwaves?

    Hi, Which frequencies does an MRI machine use? Is it microwaves? Would prolonged exposure to it be damaging to the body?
  35. W

    MSEE Electromagnetics, RF and Microwaves + ?

    The program I am looking at has an emphasis on Electromagnetics, RF and Microwaves. If I am looking at the telecommunications industry, what other exposure might be valuable? Would some course work in Signal processing or embedded systems be beneficial?
  36. S

    Do high power microwaves ionise water molecules and/or rearrange food molecules?

    Ok, this is a separate topic about Microwaves. I have come across claim that microwaved food is safe for health as long as the food is microwaved on a low power. This is because microwaves oven that are used on high power can strip ionise a water molecule and rearraange atoms in food...
  37. W

    MS Electrical Engineering (Electromagnetics, RF and Microwaves)

    I was looking at the MS (non-thesis) in EE with a focus in Electromagnetics, RF and Microwaves. I realize jobs in military and commercial sector for communications, radar, etc. What else is out there? What kind of security would this degree offer me?
  38. Y

    Where are the future background microwaves now

    In this thought experiment the sun does not run out of fuel and the Earth is still here. So in 14 billion years we will still be detecting the CMB radiation which I presume will be a bit cooler. My question is where are these microwaves that will reach us then, now.
  39. bcrowell

    Mechanisms for heating of water by microwaves

    There are four qualitatively different effects by which microwaves can heat matter: dielectric heating ionic conductivity electronic conductivity hysteresis In most foods, 1 and 2 are of approximately equal strength. 3 can occur in soot particles formed when food burns. In pure...
  40. G

    Microwaves and heating on molecular level

    hi i am currently dealing with this problem here: i have some water and want to heat it up with microwaves. how do I determine the change in temperature of the water when i just know the characteristic features of the radiation? is there an equation for it? of course this process is not...
  41. S

    Microwaves- electric field? magnetron?

    I'm curious about how microwave ovens work. I know that there is a magnetic field in the magnetron which creates the microwaves, however, I'm curious if there is an electric field in the microwave oven box itself? I'm confused by the research I've been doing online. Also, how exactly does the...
  42. D

    Interference of fibre optic signals with mobile phones' microwaves?

    I got an SMS educating people how to find out the presence of a hidden cam in a trial room of a textile showroom or bathroom. It goes like this :- "If you can't make a call in the room,the there is a hidden cam. This is due to the interference of the fibre optic with the signal transfer."...
  43. R

    Physics of Microwaves: Find Out Why Glass Gets Hot

    My physics in school says: "Air molecules are too small to be excited [by microwaves], and [they] also have no effect on glass, plastic, or ceramic." So I thought hey, let's test that! I'm glad I did. See, I put a empty glass measuring cup from the pantry into the microwave and put it on high...
  44. L

    Laser beams in the frequency range of of microwaves

    Hello people, i have got a few thoughts which i would like to share. I few month ago i foundout that there are laser beams in the frequency range of of microwaves (maser beams). (http://en.wikipedia.org/wiki/Maser) I consider the following situation: If a conducting medium (lets think...
  45. A

    Popular books about microwaves

    Hello, please, if anybody knows popular books (I mean hard copy books) on topics like microwaves, ultra-high frequencies, radars, phased arrays, vacuum tubes, please post here the references. May be it is possible to obtain electronic versions of such books (for example at books.google.com)...
  46. J

    Why Do Microwaves Only heat up Water?

    I understand that microwaves cause water in food to heat up, but I don't understand why it is only water. Why won't the say lipids or protein molecules in food heat up why is it only water. And on a related topic is there a way to use frequency to not heat up water but to lengthen the bonds...
  47. K

    How a Magnetron Produces Microwaves: A Comprehensive Guide

    I have looked all of the internet trying to find how a magnetron produces microwaves to find nothing. Can anyone tell how a magnetron produces microwaves?
  48. E

    Understanding the Metal Mesh Effect on Microwaves

    I know that the metal mesh on the microwave oven door can block microwaves because the holes are much smaller than the wavelengths. It is the same reason why some radio telescopes can be made with a mesh. What is this effect called?
  49. B

    If infared energy makes things hotter, why do microwaves use radio waves?

    If infared radiation is responsible for somethings heat, why do microwaves use radio waves?
  50. G

    Wireless, microwaves and cancer: is there a link?

    Hello from Australia, I'm extremely worried. I rarely use mobile but unfortunately I had no choice but use a prepaid wireless usb modem which uses the same technology of the mobiles here and I have been using it about 10 hours a day for the last 9 months so if WI-FI gives cancer, then I'm...