At what approximate wavelength does the range of invisible, nonionizing infrared radiation begin?

Invisible, nonionizing infrared radiation begins at approximately 800 nm. This wavelength marks the transition from visible light into the infrared spectrum, which is not visible to the human eye. The infrared range is divided into near, mid, and far-infrared, with near-infrared beginning just beyond the visible spectrum. Since nonionizing radiation does not carry enough energy to ionize atoms or molecules, it is considered safer for various applications, including laser therapies and other treatments in the field of aesthetics and medicine. Understanding this wavelength is crucial for practitioners who work with laser technology, as it helps in selecting appropriate devices for therapeutic or cosmetic procedures.

While the other wavelengths mentioned are within the ultraviolet and visible spectrum, they do not represent the correct starting point for infrared radiation. Hence, focusing on 800 nm helps clarify the boundary between visible light and the infrared spectrum.