In physics, the terms "transverse" and "longitudinal" are used to describe different types of wave motion. These terms refer to the orientation or direction of oscillation or displacement of particles or fields within a wave.
A transverse direction refers to a direction that is perpendicular or orthogonal to the direction of wave propagation. In other words, the oscillations or displacements of particles or fields in a transverse wave occur perpendicular to the direction in which the wave is traveling.
For example, in a transverse wave on a string, when a disturbance is created at one end of the string, it travels along the length of the string in a particular direction. The particles of the string then oscillate or vibrate perpendicular to the direction of the wave's motion. This means that if the wave is moving horizontally along the string, the particles of the string will oscillate up and down vertically.
Transverse waves are commonly observed in various contexts, such as electromagnetic waves (e.g., light), waves on a string or rope, and certain types of seismic waves (e.g., S-waves).
In contrast, longitudinal waves exhibit oscillations or displacements of particles or fields in the same direction as the wave's propagation. The oscillations occur parallel to the direction of wave motion. Examples of longitudinal waves include sound waves and certain types of seismic waves (e.g., P-waves).
In summary, a transverse direction refers to a direction perpendicular to the wave's propagation, where the oscillations or displacements occur in that perpendicular direction.