What is the main difference between a longitudinal wave and a transverse wave?

The main difference is the direction in which the particles vibrate compared with the wave’s direction of travel. In a transverse wave, particles move perpendicular to the wave’s motion, so choice B is correct. In a longitudinal wave, particles move parallel to the wave’s motion. Whether a wave needs a medium or travels faster depends on the type of wave and material, not on this distinction.

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