What is the term for radiation beneath the frequency we can see?

infrared


It has a longer wavelength and slower frequency than visible light.

There are lower frequencies still (microwave, shortwave, radio, VHF, UHF, etc.) but the infrared is closest to visible light.

infared light

The term for radiation beneath the frequency we can see is "infrared radiation." In order to find this answer, one can start by understanding the electromagnetic spectrum. The electromagnetic spectrum is a range of all possible frequencies of electromagnetic radiation, from radio waves to gamma rays. Visible light is just a small portion of this spectrum, with red light having the lowest frequencies and violet light having the highest frequencies that our eyes can detect.

Beyond the red end of the visible spectrum lie lower frequency waves, which we call infrared radiation. Infrared radiation has longer wavelengths than visible light, making it invisible to the human eye. It is often associated with heat and commonly used in devices such as remote controls and thermal imaging cameras.

To answer your question, one needs to know about the electromagnetic spectrum and specifically, the portion of it that is beyond the visible light spectrum.