Concept:All electromagnetic waves share the property of travelling at the same speed in a vacuum.
Explanation:X-rays and infrared rays are both electromagnetic waves, but they have different frequencies and different wavelengths.
Electromagnetic waves are transverse, not longitudinal.
Despite their differences, every electromagnetic wave travels at the speed of light in a vacuum, given by
c=3.0×108m/s.
Therefore, the common property between X-rays and infrared rays is their speed in a vacuum.
Answer:D. travel at the same speed in a vacuum
