I am curious to know a way that will make infrared pass through metals. Metals are good reflectors of infrared,can we manipulate the wave in order to make them pass through metals?.
If you have a metal that is thin enough (i.e. thinner than the infrared skin depth), then you can pass infrared light straight through. Keep in mind this would be metals with thicknesses of the order of tens to hundreds of nanometers depending on the metal. One way this could be easily achieved is careful sputtering of a metal film onto glass. Transparent conducting films somewhat fall under this type of category (though they work quite differently).
Alternatively, you can easily pass infrared light through some doped semiconductors (e.g. Silicon). These aren't as good as usual metals at conducting electricity, but can do the job in some situations.
If the idea is to take any random chunk of metal and try to pass infrared light through it, the best you can do is to drill a hole for a line-of-sight application, or fill that hole with an optical fiber when line-of-sight won't work.
A metal sheet will transmit up to about 50% of infra red incident on it, but there is a time delay and a condition:
- Assume you have a thin metal sheet (easier to imagine for purposes here), hanging in a vacuum (to do away with convection and conduction).
- Colour the metal surface black.
- Choose an infrared heating lamp with characteristics (e.g. infrared wavelength) so as to maximise heat absorption by your metal plate.
- Heat up the surface of the metal sheet from one side with the infra red lamp, so that the heated area is approximately the same as the total area of the sheet.
Gradually, the amount of infrared radiation emitted by the sheet on the none-heated side will increase. The temperature of the sheet will reach a plateau when, per unit time, the total incident infrared radiation energy equals the total emitted infrared radiation energy. This temperature depends on the power of the infrared heating lamp. At that point in time, about 50% of the infrared energy absorbed by the sheet is effectively being transmitted through the sheet.
In other words, that heat energy-saturated metal sheet is 'passing' infra red radiation through it.