# What is beyond Gamma Rays and Radiowaves in the Electromagnetic Spectrum?

The electromagnetic spectrum is commonly refered to as consisting of; Radio-waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma Rays - of increasing frequency from left to right.

But is it possible to get radiation of higher wavelength than Radio-waves, or lower wavelength than Gamma rays - does it even exist? Or could they be produced?

Most interestingly, from the Planck–Einstein relation, E = hf, how high of an energy could you get for a very very high frequency radiation?

Higher energy gamma and longer wavelength radio?

Keep in mind that the different 'kinds' are merely human labeling conventions for a spectrum that is continuous in the mathematical sense. There is no feature of "radio" that distinguishes it objectively from microwaves. We just pick a boundary on the basis of some technological limitations that apply when we decide the difference and stick labels on.

The reason there aren't labels beyond radio and gamma is that there is no real need to label those bands.

• dmckee As you know, the wavelength of radio waves refers to the current oscillation in the antenna rod and has nothing to do with the wavelength of the photons emitted from the accelerated electrons. It is a modulated radiation. So the real limit for photons is in the IR range. – HolgerFiedler May 8 '16 at 5:15
• Nonsense. High $n$ Rydberg atom transitions are a fruitful astrophysics source and they are in the microwave range. There is no lower limit on the energy of a photon. – dmckee May 8 '16 at 5:18

In addition to the answer by dmckee and to answer the question how high in energy you could get a photon it might be worth thinking about 'Gamma Ray Astronomy' where the highest energy photons are detected. The record highest photon energy observed is apparently currently 80 TeV, which corresponsds to a wavelength of $1.5 \times10^{-20}m$ wavelength (if I calculated it correctly). This is very short considering the 'size' of the hydrogen nucleus is ~$1.8\times10^{-15}$.....

...but, of course, as dmckee points out there is a continuous spectrum and no high or low energy limit to the energy of a photon.

• There is a high-energy limit to the long-range (cosmologically speaking) propagation of high-energy photons. Above about 400 TeV the cross-section for light-light interactions with the CMB suddenly begins to become significant. – dmckee May 7 '16 at 23:07
• @dmckee - thanks for comment. Again I learn from physics SE, many thanks – tom May 7 '16 at 23:11

There is a theoretical limit for how small the waves can be. it is when the waves are as long as the Planck length. But as far as I know there isn't a limit of how long the waves can be.