Why can't we see metal?

Question

Ok. Follow my thinking on this.

We can see infared... yes it's a form of light, but isn't light a form of a radio wave?

We use metal detectors to find metal. So why can't we shoot out the same wave and read it back in using a type of lens then convert that to a picture on a screen?

Something like this would be the greatest thing on Earth to the soldiers in Iraq. It could see wires inside of objects to spot IEDs at a distance.

I'm sure there is something wrong why we can't do this, so I'm just asking what that something is.

Thanks.

Yeah, I didn't mean we can see infared with our eyes. But we can with instruments.

Thanks to those who understood that.

Yeah, I didn't mean we can see infared with our eyes. But we can with instruments.

Thanks to those who understood that.

Answer 1

Light is not a form of radio wave, but rather radio waves are a form of light. We consider light to be whatever exists in the Electromagnetic spectrum, from microwaves to gamma rays, it's all "light" to an extent, as in it is pure energy and requires no medium to travel.

The technology you are talking about is in development, but it is difficult to produce because of knowing where to stop and being able to detect curvature and exact location. It's complicated stuff.

Answer 2

The general 'rule of thumb' in optics is that you can't resolve anyting smaller than about one fifth of a wavelength in whatever part of the EM spectrum you're using. This means that, at 300 MHz, you won't get enough reflection from something less than about 20 cm in cross section to be able to detect it. But at the infra-red wavelengths, there is a lot of 'noise' from everything that's warm, and most materials are fairly opaque to those wavelengths.

And a metal detector doesn't send out a 'wave'. The detector plate is actually a coil that's used as part of a tuned LC resonant circuit. When something metalic is in the magnetic field, it causes the inductance of the coil to change (due to the change in the local permeability) and therefore the oscillator changes frequency. The amount of change provides a rough estimate of the size of the object since a larger object will cause a greater frequency shift.

HTH

Doug

Answer 3

I dont have the great answer for you, but its my understanding that humans CANT see infared. There any many different spectrums of infared, look it up on YAHOO and you will see what I mean. More to yourr question - I believe the penetration of light through clothes, bags, etc would be the major problem for a signal to be established to a receiver. It sounded good while I was typing, I'm probably full of crap though.

Answer 4

In order to see inside metal enclosures you need x-rays, nor IR. I don't know if we have detectors for x-rays like we do for visible & IR. Assuming that we do, you still need a pretty strong source beam to reflect any intelligence after the scattering from passing through an enclosure twice. You can bet there are researchers working on this somewhere.

Answer 5

You are somewhat confused we can't see infrared light waves it is beyond a frequency of lightwaves visible to the human eye just like we can't see ultraviolet light. We call if black light which is because it looks black to us even though it can burn your retnas. We can't see it.

Light waves are made of photons and in the proper wave lengths they are visible to our eyes. Liight waves are NOT the same as radio waves. Radio waves are not visible to our eyes. You can't see a radio wave and you also can not hear them. You need a radio to receive them and turn them into sound waves to hear them.

The electo-magnetic waves used to detect metal are not photon (light) waves so we can not see them with or without a "special" lens. The eletro-magnetic waves used by metal detectors are turned into sound waves that's why you wear earphones with a metal detector and not magic glasses.

Answer 6

I can see metal

Answer 7

Who said we cannt see metal Iron is a metal which your car is made of!!!!!!!!