Which of the following is NOT a type of electromagnetic radiation?

Electromagnetic radiation refers to waves of the electromagnetic field that travel through space and carry energy. This category includes various types of radiation such as X-rays, ultraviolet light, and radio waves, all of which consist of oscillating electric and magnetic fields.

Sound waves, on the other hand, are not electromagnetic radiation. Instead, sound waves are mechanical waves that require a medium (like air, water, or solids) to travel through. They consist of oscillations of particles in that medium, rather than oscillations of electric and magnetic fields. Therefore, sound waves fundamentally differ from electromagnetic radiation in their nature and propagation mechanism, making it the option that does not belong to the category of electromagnetic radiation.