Which of the following is NOT a range of radiation in the electromagnetic spectrum?

Ultrasound is indeed not part of the electromagnetic spectrum. The electromagnetic spectrum encompasses a variety of radiation types, characterized by their wavelength or frequency. This includes visible light, X-radiation, and radiofrequency, all of which are forms of electromagnetic radiation.

Visible light is the portion of the spectrum that can be detected by the human eye, encompassing wavelengths from approximately 400 to 700 nanometers. X-radiation has even shorter wavelengths, making it highly energetic and capable of ionizing atoms, while radiofrequency radiation includes wavelengths from several millimeters to kilometers, used in communication technologies.

In contrast, ultrasound refers to sound waves with frequencies above the audible range for humans (typically above 20 kHz). Unlike electromagnetic waves, sound waves, including ultrasound, require a medium (such as air, water, or tissue) to propagate and do not travel through a vacuum. This fundamental difference in the nature of sound waves versus electromagnetic waves clarifies that ultrasound is not part of the electromagnetic spectrum.