Which statement describes the speed of electromagnetic waves? their speed in a vacuum is subject to forces. their speed in a vacuum is a constant value. their speed in a vacuum decreases with distance. their speed in a vacuum is subject to an observer’s motion.

Their speed in a vacuum is a constant value.

Explanation:

Electromagnetic waves consits of oscillations of electric field and magnetic field. The oscillations of these fields occur in a direction perpendicular to the direction of propagation of the waves, so they are transverse wave. Electromagnetic waves, contrary to mechanical waves, do not need a medium to propagate, so they can also travel through a vacuum. In a vacuum, their speed is constant and has always the same value, the speed of light:

inverse v=i*r

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