The lowest point of a transverse wave is called the trough. It is the point on the wave where the displacement or amplitude is at its minimum. To understand why it is called the trough, we need to visualize a transverse wave. A transverse wave is characterized by the motion of the particles being perpendicular or at right angles to the direction of wave propagation. Imagine a wave traveling horizontally from left to right. As the wave passes through a point, the particles at that point move up and down or oscillate about their equilibrium position. The highest point of this oscillation is called the crest, while the lowest point is called the trough. The terms "crest" and "trough" are borrowed from the analogy of waves in water, where the crest corresponds to the highest point of a wave on the surface, and the trough is the lowest point between two adjacent waves.
