# EM spectrum

#### Jack

Is there an electromagnetic wave with a higher frequency than that of of gamma rays?

Is is possible for us to change the frequency of a wave?

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#### russ_watters

Mentor
Originally posted by Jack
Is there an electromagnetic wave with a higher frequency than that of of gamma rays?

Is is possible for us to change the frequency of a wave?
I think gamma waves are as high as they get, but I'm not sure.

The frequency of a wave can be changed through interaction wih gravity or doppler shift. I think those are the only ways.

#### Mike H

Most EM spectrum tend to cut off at gamma rays since that's about the most energetic radiation we see, but in principle you could have EM radiation with smaller wavelengths.

Am guessing that you're not referring to reradiated EM waves (e.g. light is absorbed by some material and then reradiated at a lower frequency OR sum frequency generation), nor some experimental laser techniques where you're working with entire pulses of laser light, so am not sure otherwise on the second part of the original post.

#### chroot

Staff Emeritus
Gold Member
The term 'gamma' refers to any EM radiation with energy greater than about 100 keV. It is unbounded -- any photon with energy > 100 keV is gamma radiation.

- Warren

#### Jack

What is heat radiated out from a hot object as?

#### chroot

Staff Emeritus
Gold Member
You can easily calculate the peak of the blackbody spectrum for any given temperature; that will give you a rough idea of the dominant frequency radiated by any thermal body at that temperature.

- Warren

#### mark726

Chroot, don't you do that by using Wien's law? Then you can just do Peak Wavelength=(2.9*10^7)/T. T is in kelvins, and then the peak comes out in angstroms.

There are higher energy photons beyond gamma rays, they are called cosmic rays, some people put that in the same class as gamma though, but some sources set it apart. Whatever, its a matter of semantics, but if you're used to thinking of a gamma ray as something that we can produce on earth then you should know that in this cosmic ray regime, you can't produce them with any machine yet. They come from space and when they enter the atmosphere cause "cosmic ray air showers" which is a shower of muons electrons and other stuff that comes down to the surface when the photon collides with an atom in the upper atmosphere. There is a very small flux of really really really high energy cosmic ray that is so high energy that physicists have trouble explaining where it comes from because no known mechanism in the universe should be able to produce such energetic photons.

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#### climbhi

For more info on the very high energy cosmic rays that grady is talking about please check out this site from my universities website. This project which is responsible for observing that "very small flux of really really really high energy cosmic rays" was kind of spurred on by my department and is one of their big proud achievements. They have lectures on it all the time here, its really pretty neat.

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