[Darren]

Is it possible to convert EM waves of one type to another type? Like gamma rays to x rays for example?
I found out that maybe it will not be possible because photons are bundles of fixed energy and they exist as wave packets with a specific amount of energy, no more, no less than that amount. And since E=hf, the energy remains constant and cannot change, frequency also remains constant. And since v=f lumbda, EM waves of one type cant be changed into other types of EM waves. Is this totally correct? If not, how can EM waves be changed in their frequencies?

[AWK]

http://en.wikipedia.org/wiki/Scintillator

[Darren]

Oh what i actually wanted is whether there is any way to change the frequency of EM waves directly, without being absorbed by any object or atom and then re emitting another photon of different frequency.

[AWK]

Probably it is  impossible.

[DrCMS]

Oh what i actually wanted is whether there is any way to change the frequency of EM waves directly, without being absorbed by any object or atom and then re emitting another photon of different frequency.

With out the EM wave interacting with anything how is it going to change?

[Darren]

Oh what i actually wanted is whether there is any way to change the frequency of EM waves directly, without being absorbed by any object or atom and then re emitting another photon of different frequency.

With out the EM wave interacting with anything how is it going to change?

The basis of my question is: when gamma rays travel through space, can they interact with gases and particles in space and lose energy? And after some distance, their frequency of the EM wave will decrease?

[Enthalpy]

This happens all the time, see the Compton effect for instacne. But this IS called an interaction.

The direction of propagation is changed as well, and when a gamma has lost energy once, the remnant (or the new gamma of lesser energy) is absorbed quickly. So please do NOT try to explain the redshift that way.

[manonemission]

This happens all the time, see the Compton effect for instacne. But this IS called an interaction.

The direction of propagation is changed as well, and when a gamma has lost energy once, the remnant (or the new gamma of lesser energy) is absorbed quickly. So please do NOT try to explain the redshift that way.

I wonder if redshift due to gravitational fields should be called an "interaction."  Technically, absorption and re-emission by electrons is just interaction with EM fields, right?

[gippgig]

See "frequency doubling" (but not (at least not yet) for gamma rays).