# Electromagnetic spectrum

1. Aug 3, 2004

### µ³

Is there a frequency below radio waves or above gamma rays? What makes radio waves and gamma rays the bounds of the electromagnetic spectrum?

2. Aug 3, 2004

### pallidin

Good question.
I am sure someone has the answer.
One thing I read, not sure if it is true, is that frequencies going lower will eventualy "flatline" to zero frequency. Not sure what happens on increasing frequencies.

3. Aug 3, 2004

### Nenad

there is no limit to frequencys. They can be as high as gamma rays and higher and as low as radio or lower. All it is is differences in wavelength or elecromagnetic spectrum. This is what I think, I might ne wrong but it makes sence to me to think if it this way.

4. Aug 3, 2004

### Claude Bile

Very Low Frequency radio waves are used (or at least they used to be) to communicate with submarines. The frequency of these waves was less than 1 kHz (not sure what the lower bound was). One could also consider that the absence of any e/m radiation (or a constant e field) can be thought of as an e/m wave with a frequency of 0 Hz! Can't get lower than that.

You cannot go arbitrarily high in frequency since frequency in e/m waves is a measure of the photon's energy, you can only generate a photon with a given frequency if there is enough energy to do so.

Claude.

5. Aug 3, 2004

### µ³

My question is: what are the lower and upper theoretical limits in which EM waves can exist. I think that at certain high velocities when you collide a positron with an electron you don't get a photon (gamma ray) but get Z0 Boson. Is there any other mechanisms for generating photons that would generate them at higher frequencies/energies than a positron-electron collision?

6. Aug 4, 2004

### ArmoSkater87

im pretty sure that supernovas generate very high frequency e/m radiation.

7. Aug 4, 2004

### Gonzolo

Radio waves contain everything between microwaves and DC (constant field), which is infinite wave length (or 0 frequency). That's all called radio. To make an extremely low frequency wave, charge up a balloon with static and move it as slow as you want.

As for the upper limit, any photon with a greater frequency than x-ray is gamma. When it energy is sufficient (frequency high enough), a photon can spontaneously become a pair of electron and positron (mass, E=mc2, f = mc2/h). Put in two times the mass of an electron in this equation and this a nice upper limit for my needs. I think photons with greater energies can be obtained by smashing atoms. I suspect the upper limits are defined by the probability of a photon of becoming other massive particles. A fundamental limit must be whatever energy the first photons after the Big Bang had.

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