Is Teraherz Radiation New?

Regarding the future applications of terahertz technology, I thought we already knew the entire electromagnetic spectrum. In fact we do not, terahertz lies between microwaves and infrared radiation. The future applications of this is astonishing. For example, faster communications and next generation scanning and imaging technologies. The TSA will pretty much be out of a job, because T-Ray(terahertz) scanners will automatically detect chemical weapons and bombs. I know this because they leave a trace on the terahertz spectrum. The downside with communications is terahertz is absorbed easily by the Earth's atmosphere, so the communications cannot be too high in the sky. What I am asking is, are there any other frequencies on the electromagnetic spectrum we might discover? I was taught in school, that there are radio waves, microwaves, infrared, visible, ultra violent, x-rays, and gamma rays. Now the books have to be rewritten because of the existence of terahertz or t-rays. Remember it lies right between microwaves and infrared radiation. Another question is what about sound? So far there is infra sound, sound, and ultrasound. Do you think in the future we will discover other types of sound? Sorry for the length of my question, as you can see I know a lot about science and technology.
- Nehemiah (age 23)
Indiana

That question raises the important differences between rough verbal names that we give things and the more precise mathematical descriptions at the core of physics. Teraherz electromagnetic waves were always understood, starting from Maxwell's discovery (~1864) of the equations describing electromagnetism. All the different frequencies of those waves are described by exactly the same equations and follow the same patterns. The different names you mention ("radio waves, microwaves, infrared, visible, ultra violent, x-rays, and gamma rays") are just rough divisions of the full spectrum into different ranges, and have no particular deep meaning. The teraherz range was included as part of the far infrared in the traditional naming regime. Now that some convenient teraherz sources are available, and some interesting applications, people have started using a special name for that range rather than lumping it in a bigger category.

The same principle applies to sound. The possible frequencies are continuous, with no missing gaps. Exactly where people draw the lines between the different names chosen doesn't affect the behavior of the waves. If "ultrasound" means sound at frequencies higher than audible, it would have started at around 20kHz when I was young. Now it would be more like 12kHz. My ears have changed, but the sound waves haven't.

Mike W.

(published on 01/19/2014)