Terahertz to megahertz: what a scanner can and cannot see
What this conversion does
It multiplies by a million, moving a frequency from the unit the imaging literature uses into the unit the instrument's radio-frequency hardware is specified in. The two halves of a terahertz scanner operate in different notations: the source is described by physicists in terahertz, the multiplier chain that feeds it by engineers in megahertz. The conversion is what lets one specification be read against the other.
Why the band is useful for imaging
Radiation in this region passes through dry, non-conducting materials such as clothing, paper and some plastics, but is absorbed by water and reflected by metal. That combination makes it useful for seeing through packaging and for identifying concealed objects without the ionising risk of X-rays. Its limitation is equally clear: anything wet is opaque, so the technique does not see through people or through damp material.
Terahertz to megahertz conversion table
Instrument frequencies in both units, showing how a scanner described in terahertz is built from components specified in much smaller numbers.
| Terahertz (THz) | Megahertz (MHz) |
|---|---|
| 1 | 1000000 |
| 2 | 2000000 |
| 10 | 10000000 |
| 100 | 100000000 |
| 300 | 300000000 |
| 1000 | 1000000000 |
Resolution and frequency are linked
The shortest detail an image can resolve is limited by the wavelength, and shorter wavelengths give finer images. Since terahertz wavelengths are around a millimetre, the resolution of a scanner is roughly at that scale — enough to identify a shape, not enough to read a document. That single relationship explains both what the technique is used for and what it cannot be asked to do.
Six places, one step
Multiplying by a million moves the decimal point six places, so 0.3 becomes 300,000. The pattern to remember is that a value below one terahertz always converts to a megahertz figure in the hundreds of thousands or lower — never in the billions.
Frequently asked questions
How do I convert terahertz to megahertz?
Multiply by a million. So 0.3 THz is 300,000 MHz, and 1 THz is 1,000,000 MHz. The conversion crosses two prefix steps, gigahertz among them, in one multiplication.
What can terahertz imaging see through?
Dry, non-conducting materials such as clothing, paper, cardboard and many plastics. Water absorbs strongly in this band, so anything damp is opaque, and metal reflects rather than transmits, which is precisely what makes concealed objects visible against the background.
Is terahertz scanning safe?
The radiation is non-ionising, unlike X-rays, so it cannot break chemical bonds directly, and each photon carries far less energy than visible light. That is the main reason it is attractive for screening people. Exposure limits and local regulations still apply to any equipment.
Why is the image resolution limited?
Because resolution is bounded by the wavelength, and terahertz wavelengths are around a millimetre. The image can therefore show shapes and outlines at roughly that scale but cannot resolve fine print or small surface detail.
Why does a scanner need a megahertz specification?
Because a terahertz source is often built by multiplying up from a lower-frequency oscillator, and those stages are designed and measured in megahertz. The frequency conversion is what connects the design of the electronics to the performance of the finished instrument.