# How short can electromagnetic radiation become? Shorter than gamma rays?

#### Doug1943

is there some physical limit on the wavelength of electromagnetic radiation? Can there be radiation shorter than gamma rays?

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#### RPinPA

Homework Helper
No, because gamma has no lower bound on the wavelength. If it's shorter than X-rays, it's called gamma rays. Just as everything at the other end of the spectrum is called "radio waves" and there's no limit on how long those wavelengths can be. They're still called "radio".

#### Drakkith

Staff Emeritus
2018 Award
There is no known limit on how short the wavelength of an EM wave can become. Everything past a certain frequency is either x-rays (if they originate from outside an atomic nucleus) or gamma rays (if they originate from the decay of an atomic nucleus).

#### PeterDonis

Mentor
Moderator's note: Moved thread to Classical Physics forum.

#### jim mcnamara

Mentor
The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length (1.616255(18)×10−35 m)
From https://en.wikipedia.org/wiki/Electromagnetic_spectrum
which cites Bakshi, U. A.; Godse, A. P. (2009). Basic Electronics Engineering. Technical Publications. pp. 8–10

#### Klystron

Gold Member
The continuity of the electromagnetic spectrum may be one of the most beautiful discoveries in physics. From the same source as above:
Note that there are no precisely defined boundaries between the bands of the electromagnetic spectrum; rather they fade into each other like the bands in a rainbow (which is the sub-spectrum of visible light).
Practical boundaries arise from technology. We can ask given current technology, what is the highest frequency -- shortest wavelength signal -- human devices can generate? Or that we can detect and at what energy?

#### sophiecentaur

Gold Member
The continuity of the electromagnetic spectrum may be one of the most beautiful discoveries in physics. From the same source as above:

Practical boundaries arise from technology. We can ask given current technology, what is the highest frequency -- shortest wavelength signal -- human devices can generate? Or that we can detect and at what energy?
This assumes that human measurement is a requirement. I think the OP probably had in mind processes taking place in conditions that are too extreme to allow measurement. This takes us into the sort of situations where String Theory could be tested and beyond and we don't yet have the ability to go there.

#### artis

and just by curiosity what would be some of those processes where string theory could be tested @sophiecentaur ?

"How short can electromagnetic radiation become? Shorter than gamma rays?"

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