Electromagnetic waves are characterized by their wavelength. I am wondering whether there are any limits in the range of the wavelength.
Not as far as anyone knows, except that there is may be an upper limit (lower limit of wavelength) where the photon would contain all the energy of the known universe. However, I think it still may be possible for that virtual photon to exist for a very short time without breaking any rules. Very long wavelength photons contain very little energy and probably there is no reason why very slow or low-energy events shouldn't radiate them.
Wavelength or frequency? If it is the first, we should not forget about spatial harmonics in the dispersive systems, which propagate at the same frequency, but different wavelengths. And there can be infinte number of them (like in Fourier series).
as already mentioned in the previous comments we have to discriminate between (propagating) waves in free space with v=c and EM waves in some dielectric /magnetic media where the wavelength is shorter compared to free space. At the high end you may talk about very hard gamma rays in the ballpark of Giga electron Volts and at the low end say something in the range of a few micro Hz..(certain people in the axion community are talking about such waves).Among the lowest practical wavelength /frequency on earth we have the Schumann resonances (between earth and ionophere) starting at 7 Hz.
Dear Jonghoon Kang ,
The lowest EM wave frequency requires an oscillator whose frequency is as small as possible may be millihertz. At this frequency you need an antenna to be an efficient one it must be of the size Lambda/4. To get an imagination about it
lambda= 3x10^5 km/ .001= 3x 10^8 km =300 million km
The distance between sun and earth=147.42 million km
Then lambda/4= 75 million km which is the half the distance from the earth to sun. If one to use a loop antenna it size may be the circumference of the earth and still its radiation efficiency will be very low.
In order to observe the radiation for the far field one needs at least a distance of lambda. That it is will be observed at the sun surface.
For us the communication engineer one uses the medium waves in sound broad casting. Its frequency is from 3oo to 3000 kHz. Even the broad cast frequency is restricted to 550kHGz.
As you see the main difficulty is the antenna to convert the rf signals into EM waves.
Another possibility of generating very low frequency EM waves is by a black body radiation. As the size of this body increases it may emit at the low frequencies.
One can imagine a huge star may emit low radio frequencies. The problem may be is to be able to detect such radiation.
The highest frequencies of the observed EM radiation is for the Gamma rays.
As the photon energy increases its behavior approaches that of the mass which means that its photon will be more concentrated in the space.
Best wishes
Dear Abdelhalim,
as you say correctly..the antenna should preferably be lamda/4 or bigger but it can work also quite well when its much smaller provided its made resonant; there are many good books on electrically small antennae..and remember: a normal AM medium wave or long wave radio is usually smaller than 20 cm and thus also the inbuild ( often resonant) ferrite antenna..and it still works reasonably well and for submarine communication about 30 years ago electrically small antennae were build and used around 70 Hertz
Dear Fritz Caspers ,
Thank you for extending my answer that one can use short antenna than may be as small as lambda by 10 or one can use loop antennas with magnetic core materials. I am a communication engineer and I am aware of the the antenna.
Any way thank you for your extension. In my answer I hinted the use of much smaller loop antennas. I just wanted to show it is the matter of the antennas that may limit the efficient radiation at low frequencies.
Best wishes
Here is a new understanding of different photon wavelengths.
The key evidence for light waves is the Young’s double-slit interference experiment. After the discovery of the double-slit interference experiment of particles (electrons, etc.), the conclusion of light waves can no longer be established. "Wave-particle duality" denies light as particles because of the wave phenomenon, but recognizes the wave nature of particles. It is better understood that light particles have wave phenomena. Of course, light particle behavior and wave mechanism need new understanding.
https://book4you.org/book/18269199/bf2351
The electric field of a charged particle has no force on itself, indicating that the electrostatic effect is the effect between the charged particles, not the effect between the field and the charged particle, and the electric field is an active field. Similarly, the magnetic field is also an active field. There are no flying passive electromagnetic fields (electromagnetic waves), light is a particle.
The electric field of an electron has no force on itself, and the field does not exist alone. Photons are electromagnetic particles, Wavelength is a force balance structure, and electromagnetic theory is a useful mathematics.
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