The electromagnetic spectrum is described as which of the following?

• A. The electromagnetic spectrum is the range of all electromagnetic frequencies, including radio waves, microwaves, infrared waves, visible light, ultraviolet light, x-rays and gamma rays.
• B. The spectrum describes sounds in air.
• C. The spectrum includes only visible light.
• D. The spectrum is made of waves that require a medium to travel.

Answer: (A)

All electromagnetic radiation spans a range of frequencies and wavelengths, from long radio waves to short gamma rays. These waves are oscillating electric and magnetic fields that can travel through space without needing a material medium, forming a continuous spectrum. The spectrum thus includes radio, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Sounds in air are mechanical waves, not electromagnetic, so they aren’t part of this spectrum. The spectrum also isn’t limited to what we can see with our eyes—visible light is just a small portion of the whole. And unlike mechanical waves, electromagnetic waves don’t require a medium to travel through.