# What is the highest frequency of electromagnetic radiation?

• I
Title says it all.

Also, if the frequency of electromagnetic radiation is limited, why? My guess is the wavelength is limited to the Planck length, and when I plug those numbers into the calculator, I get 1.855 * 10^43 Hz. The maximum (Edit: observed) frequency of a gamma ray is 3 * 10^20 Hz though.

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PeterDonis
Mentor
Title says it all.

And here is the short answer: we don't know.

My guess is the wavelength is limited to the Planck length

This is a fairly common speculation in quantum gravity, but we don't have a confirmed theory of quantum gravity so we don't know if this speculation is correct.

The maximum frequency of a gamma ray is 3 * 10^20 Hz though.

You mean, the highest frequency of a gamma ray that we have observed is 3 * 10^20 Hz. That doesn't mean that's the highest frequency that is physically possible.

• vanhees71 and enter
And here is the short answer: we don't know.

This is a fairly common speculation in quantum gravity, but we don't have a confirmed theory of quantum gravity so we don't know if this speculation is correct.

You mean, the highest frequency of a gamma ray that we have observed is 3 * 10^20 Hz. That doesn't mean that's the highest frequency that is physically possible.
Yeah, I misstated the gamma ray part.

I don't understand, how is quantum gravity related to this?

PeterDonis
Mentor
how is quantum gravity related to this?

It's related to your guess that the minimum wavelength for EM radiation is related to the Planck length, as I said in post #2.