Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli moving rapidly and randomly through the field of view, changing directions after a brief tumble and taking off in a different direction. These cells are exhibiting motility.

Swimming

Explanation:

The swimming motility is one of the type of bacterial movement. This bacterial movement is mediated by the rotating flagella. It takes place when the individual cells move in the liquid environment.

The phase contrast microscope is used to the enhance the contrast of the images formed by the ordinary light microscope. This can be used for observing the transparent and colorless specimens. The phase contrast microscope enables the visualization of the cells and their organelles that would be difficult to observe under the ordinary light microscope.

The phase contrast microscope can also help in observing the swimming motility of the bacteria. This can be used to observe the change in directions of the bacilli under microscope.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave