Hertz to terahertz: the top of the useful spectrum
What this conversion does
It divides a frequency by a trillion. The result is usually a small decimal, because terahertz is a very large unit: a signal of ordinary radio frequency becomes a number with a dozen leading zeroes. The tool writes those in exponent form rather than as a long string of zeroes, so the significant digits stay visible instead of being buried.
Why terahertz is a spectroscopy unit
Between the microwave bands and the infrared there is a stretch of the spectrum where neither electronics nor optics worked well for a long time. Its frequencies are around a trillion cycles per second, which is the range where many molecules rotate and vibrate, so it carries a fingerprint of what a material is made of. Writing those frequencies in hertz is impractical, which is why the unit exists and why a single hertz is such an insignificant fraction of it.
Hertz to terahertz conversion table
Spectroscopy landmarks in both units, showing the point at which the hertz column stops being a number anyone would write down.
| Hertz (Hz) | Terahertz (THz) |
|---|---|
| 1 | 1e-12 |
| 50 | 5e-11 |
| 60 | 6e-11 |
| 440 | 4.4e-10 |
| 1000 | 1e-9 |
| 20000 | 2e-8 |
| 100000 | 1e-7 |
The gap in the middle of the spectrum
Below the gap, signals are generated by oscillating electrons and read with an antenna. Above it, they are generated by transitions in atoms and read with a lens. Each approach works well at its own end and poorly in the middle. Terahertz sits in that middle, which is why it took decades longer to become useful than the bands on either side of it.
Read the exponent, not the zeroes
A frequency of 1 Hz written in terahertz has twelve decimal places, and counting them by eye is a reliable way to make an error of a factor of ten. Exponent notation removes that step: the exponent is the number of places, stated outright.
Frequently asked questions
How many hertz are in one terahertz?
One trillion, which is a million million. The prefix steps up by a factor of a thousand four times from hertz: kilo, mega, giga, tera. So 1 THz is 1000 GHz, a million MHz and 1,000,000,000,000 Hz.
Why does 1 Hz become such a small number in terahertz?
Because a terahertz is enormous compared with an ordinary frequency. One hertz is one trillionth of a terahertz, which the converter writes in exponent form. The value is not being rounded to zero — it is exactly one trillionth, and every digit is preserved.
What is the terahertz gap?
The band of the spectrum, roughly between 0.1 and 10 THz, where neither conventional electronics nor ordinary optics work efficiently. It sits above the fastest transistors and below the longest infrared lasers, and it is only recently that practical sources and detectors have become available.
What is terahertz used for?
Molecular spectroscopy, where the frequency identifies a substance; non-destructive imaging, because terahertz radiation passes through clothing and paper but is absorbed differently by different materials; and some medical and security scanning applications that exploit the same property.
Is terahertz radiation dangerous?
It is non-ionising, so it does not break chemical bonds the way X-rays do, and it carries far less energy per photon than visible light. That is a large part of why it is attractive for scanning applications. As with any radiation, exposure limits and local rules still apply.