The blank is the bottom part of a transverse wave
The blank you are referring to is called the trough. It is the lowest point on a transverse wave and represents the negative displacement from the equilibrium position. To understand how to identify the trough, let's first review what a transverse wave is.
A transverse wave is a type of wave where the particles of the medium oscillate perpendicular to the direction of wave propagation. In other words, the particles move up and down or side to side, while the wave itself moves forward. Examples of transverse waves include water waves, electromagnetic waves (such as light and radio waves), and seismic S-waves.
To identify the trough on a transverse wave, you need to look for the lowest point in the wave pattern. Imagine a wave on a graph where the x-axis represents distance and the y-axis represents displacement. The highest point on the wave is called the crest, and the lowest point is the trough. The crest corresponds to the peak positive displacement from the equilibrium position, while the trough corresponds to the peak negative displacement.
In practical terms, if you have a physical representation of a transverse wave, such as a rope being shaken up and down, you simply need to locate the lowest point reached by the rope during one complete wave cycle. That point is the trough.
Understanding the characteristics and components of waves helps us describe and analyze various phenomena in science and everyday life.