Answer:
in a vacuum
Explanation:
Electromagnetic waves are waves consisting of oscillations of electric and magnetic fields along a plane perpendicular to the direction of propagation of the wave (transverse waves)
Electromagnetic waves are the only waves being able to travel in a vacuum, since they do not need a medium to propagate.
In a vacuum, all electromagnetic waves travel at the same speed, called speed of light, whose value is:
The speed of the waves is actually reduced when they enter a medium, according to
where n is the refractive index of the medium.
Electromagnetic waves are also classified into 7 different types according to their wavelength. From shortest to longest wavelength, we have:
Gamma rays
X-rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves