Answer:
Electromagnetic waves travel in a vacuum with a definite and unchanging speed.
When electromagnetic waves travel in vacuum, there is a definite, constant ratio between the magnitudes of the electric and magnetic fields.
Step-by-step explanation:
Electromagnetic waves are waves that come about due to the vibrations generated between an electric field and a magnetic field. There is presence of oscillating magnetic and electric fields and the two statements mentioned above best describes it's properties.