TDP can emit wavelengths from 2 to 25 micrometers, different from other wavelengths, such as visible rays and x-rays, etc. Why is TDP so distinctive in the medical field? First, we shall depict the relations of wave range of TDP to the sun's rays in the biological field. The surface temperature of the sun is about 5500°C, the maximum peak range being at 5000°C. We are already aware that the sun ray intensity is 100 milliwatts (mw) per square centimeter (cm²) in the sea surface (earth). The sun radiation intensity detected by satellite is 135 mw/cm². Therefore, the difference between the earth's surface (E₁) and the sky (E₂) is:

There are hundreds of miles in distance between the earth and its satellite, yet the distance is very small when compared to the distance between the earth and the sun, so the sun ray intensity should be similar between the earth's surface and the satellite. Why does a 34 mw difference exist? The reason is mainly because the atmosphere contains a large anount of water vapor (CO₂, O₃, etc.) These various gases can partially or totally absorb the sun's rays in a certain wavelength range. That is the reason we do not receive them. There are three "windows", which permit the sun's rays to pass through the atoosphere and reach the earth's surface (see Figure 1). These wavelength ranges are: 0.3 to 2.5 micrometer, 3 to 5 micrometer, and 8 to 14 micrometer. The range of 5 to 8 micrometers is missing, yet plays an inportant role in the biological field depicted aa follows:

Wavelength (micrometer)

Figure 1 - Sun Ray Spectrum at 1000 Feet Above Sea Level

TDP propagation lies between 2 to 25 micrometers. In normal conditions the peak range of human emission falls around 9 micrometers. The two emission levels (Human and TDP) have a broad overlapping area between 4 to 15 micrometers. Humans are able to absorb, selectively, certain wavelengths, including wavelengths in the missing range of 5 to 8 micrometers. These wavelengths may create a very strong biological eEfect although the portions are comparatively small.

The propagation intensity is reverse relative to the distance. In 27 cm of distance between TDP plate and human skin the power intensity is only 35 mw per cm² for one hour period, skin temperature is 38.8°C which is well tolerated by humans.

Further research on people has concluded that they can absorb 3 to 4 micrometer wavelengths mainly due to the hydrogen-oxygen bonds and the carbon-hydrogen bonds. Wavelengths between 5.9 to 11.0 micrometers are due to the absorbance of single and double carbon-hydrogen bonds, and single and double carbon-oxygen bonds. 13 to 15 micrometers are due to amino acid bonds. So there ls a reason why we absorption different wavelengths.