7.4.1—That all electromagnetic waves are transverse waves that travel with the

Electromagnetic waves consist of mutually perpendicular electric and magnetic fields, both transverse to the direction of travel, and move at c≈3.00×10⁸ m s⁻¹ in vacuum.

They do not require a material medium; in matter their speed can be lower and depends on the medium.

Radio, visible light and X-rays are different frequencies of the same transverse electromagnetic family.

“Electromagnetic” does not mean longitudinal, and c applies to free space, not every material.