A wave traveling in a straight line is described as which type?

• A. Longitudinal
• B. Transverse
• C. Circular
• D. Spin

Answer: (A)

When a wave is described by how the medium’s particles move relative to the direction of travel, the key distinction is between motion along the propagation direction and motion perpendicular to it. If the particles oscillate in the same direction as the wave travels, the wave is longitudinal. In longitudinal waves, the medium undergoes compressions and rarefactions along the path of travel, so energy moves forward as the particles push and pull in that same direction. This is the behavior of sound waves in air and in soft tissues used in ultrasound imaging, where the wave travels straight ahead and the particle motion is along that line.

Transverse waves have particle motion perpendicular to the direction of travel (like waves on a string or light waves in free space), which isn’t implied by a simple straight-line propagation in this context. Circular waves describe energy spreading outward in circles around a source, not a single straight-line propagation, and spin isn’t a standard wave type.

So, a wave moving in a straight line in this context is best described as longitudinal.