AFOQT Practice Test

Which of the following is true about electromagnetic waves?

1. They require a medium to travel through

2. They are composed of oscillating electric and magnetic fields

3. They only travel in a vacuum

4. They are always visible to the human eye

The correct answer is: They are composed of oscillating electric and magnetic fields

The assertion that electromagnetic waves are composed of oscillating electric and magnetic fields is indeed correct. Electromagnetic waves consist of alternating electric and magnetic fields that are perpendicular to each other and to the direction of wave propagation. This foundational characteristic of electromagnetic waves allows them to transmit energy through space. Electromagnetic waves can travel through various mediums, but they do not require a material medium, which differentiates them from mechanical waves that need a medium (like sound). They can propagate through a vacuum, but this is not the only condition under which they exist. While electromagnetic waves cover a broad spectrum—including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays—only a small portion of this spectrum (the visible range) can be seen by the human eye. Thus, claiming they are always visible is incorrect. Understanding that option B accurately describes the nature of electromagnetic waves is key to grasping how they operate within the realms of physics and engineering.