User talk:Anoel333

=RF and Ultrasound= Hello Anoel333, I hope you find this message. First of all, welcome to wikipedia. No, I don't mind you asking - but a good way to ask people questions on wikipedia is via their talk page (i.e. this is your talk page - mine is at User talk:GyroMagician). It's a place where you can leave any kind of message for another editor. But you've found me, so all is well.

Now, to your question. Ultrasound is basically sound, but at a higher frequency than humans can hear. We hear in roughly the range 20-20kHz (1Hz = 1 cycle per second). Ultrasound is anything higher frequency than that - medical ultrasound in typically in the 2-20MHz range, so well above our hearing range. Sound waves are pressure waves. If you speak to me, the sound transfers from your mouth to my ears as a pressure wave in the air. Pressure waves travel well through liquid and solids too, making both medical imaging and nondestructive testing possible. The phrase "in space, nobody can hear you scream" is true, because there is no medium to carry the sound/pressure wave.

Radio frequency almost always means electromagnetic waves - that is, a wave that alternates between magnetic and electric energy. Visible light is the most common example (100s of Terahertz), but also what is transmitted to your radio receiver (kHz to MHz) and x-rays (even higher frequency than light). Electromagnetic waves do not need a medium to propagate through, so will happily pass through space (or our days would be rather dark!).

I'm not sure what kind of application you're interested in. There are basically two routes - you want to see something (imaging), or you want to do something. You can do either with both kinds of wave. Ultrasound can be used in low intensity for imaging, or higher intensities for something like thermal ablation (basically burning out something you want to remove). You can do the same with RF. Both methods work by focusing energy in one spot, to heat it up. RF can also be used for imaging, such as in MRI (that's a bit more complicated), or those new body scanners in airports that 'see through clothes'. It's similar to shining a light through someone, but radio frequencies travel though bodies more easily than light does.

Does that help? I could write an essay here, but I think it will be more useful if you direct me a bit ;-) You can answer by editing this page (hit the edit tab at the top of the page) - and I'm now watching this page, so I'll see if you make a change. GyroMagician (talk) 22:39, 28 April 2010 (UTC)