Which type of waves have sideways vibrations?

Transverse waves are characterized by vibrations that occur perpendicular to the direction of wave propagation. This means that if the wave is moving horizontally, the particles of the medium through which the wave travels vibrate up and down, creating sideways vibrations.

This distinction is key in understanding how different types of waves behave. For example, in a stringed instrument, when you pluck a guitar string, the wave that travels along the string is a transverse wave.

In contrast, longitudinal waves, such as sound waves, have particles vibrating parallel to the wave's direction of travel, resulting in compressions and rarefactions along the same direction. Mechanical waves, which encompass both transverse and longitudinal forms, do not specifically refer to the direction of vibration. Surface waves, which typically occur at the interface between two different mediums (like water and air), involve both longitudinal and transverse motions, but they do not solely represent sideways vibrations.

Thus, transverse waves are clearly defined by their perpendicular motion, making them the correct choice in this context.