A Level Physics Practice Exam

How do longitudinal waves differ from transverse waves?

1. Points oscillate perpendicular to direction of wave

2. Points do not oscillate

3. Points oscillate in line with the direction the wave travels

4. Points oscillate in a circular motion

The correct answer is: Points oscillate in line with the direction the wave travels

Longitudinal waves are characterized by the oscillation of points in the medium being parallel to the direction in which the wave travels. When a longitudinal wave passes through a medium, such as sound waves in air, the particles of the medium compress and rarefy in the same direction as the wave is moving. This back-and-forth motion of particles along the same line as the wave propagation creates regions of compression and rarefaction. In contrast, transverse waves involve oscillations that occur perpendicular to the direction of wave travel. For instance, in water waves or light waves, the movement is up-and-down or side-to-side relative to the direction of wave travel. It's worth noting that the other provided options do not accurately describe the behavior of longitudinal waves. For instance, the idea that points do not oscillate implies a stagnant medium, which does not occur in a wave context, as waves require the oscillation of particles to transmit energy. Circular motion of points would be characteristic of surface waves, such as water waves, where particles move in a circular path rather than a linear compression and rarefaction pattern. Thus, the correct understanding revolves around how points in a longitudinal wave oscillate in line with the wave direction.