Answer:
Radio waves
Explanation:
Electromagnetic waves consist of periodic oscillations of electric and magnetic fields in a plane perpendicular to the direction of propagation of the wave.
Electromagnetic waves are the only waves able to travel in a vacuum, where they travel with a speed of
[tex]c=3.0\cdot 10^8 m/s[/tex] (speed of light).
Electromagnetic waves are also classified into 7 different types, depending on their wavelength.
From shortest to longest wavelength, we have:
Gamma rays
X-rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves
Radio waves are the EM waves with longest wavelenght, spanning from a few meters to several kilometers. Because of this property, radio waves are able to travel across long distances without being absorbed by anything: so, they are used to detect distant objects such as stars and galaxies, due to this property.
