Electromagnetic wave

AP Physics 2 EK 14.4.A.1: electromagnetic waves consist of oscillating electric and magnetic fields that are mutually perpendicular. EK 14.4.A.1.i: they are transverse, because both field oscillations are perpendicular to the direction of propagation. EK 14.4.A.1.ii adds that they are commonly assumed to be plane waves, characterized by planar wave fronts.

No medium required. EK 14.4.A.2 states it outright, and that is the line separating an electromagnetic wave from a sound wave. EK 14.1.A.3.i gives the vacuum speed as a universal physical constant, $c = 3.00 \times 10^8$ m/s.

The electromagnetic spectrum. EK 14.4.A.3 says categories of electromagnetic waves are characterized by their wavelengths. In order of decreasing wavelength (EK 14.4.A.3.i): radio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays. Visible light splits the same way (EK 14.4.A.3.ii): red, orange, yellow, green, blue, violet. Decreasing wavelength means increasing frequency, since $\lambda = c/f$.

The Topic 14.4 boundary statement sets the depth: AP Physics 2 expects students to know the ordering of the electromagnetic spectrum, including visible light, but students will not be expected to define exact wavelength ranges within the spectrum. Learn the order, not the nanometer bands.

EK 14.4.A.3.iii notes that electromagnetic waves of all wavelengths are sometimes collectively called light or electromagnetic radiation.