In M-mode, a line that moves up and down on the display indicates what about the reflector's motion?

In M-mode, a line that moves up and down on the display indicates what about the reflector's motion?

• A. It is rotating
• B. It is stationary
• C. It is moving closer to and farther from the transducer
• D. It is moving purely laterally

Answer: (C)

In M-mode, time is plotted along the horizontal axis and depth (distance from the transducer) along the vertical axis, so you’re watching how far away a reflector is over time. If a reflector moves toward the transducer, its depth decreases and the echo trace moves upward on the screen; if it moves away, the depth increases and the trace moves downward. Therefore, a line that moves up and down shows the reflector is moving along the beam axis—closer to and farther from the transducer. If the object moved only laterally, its depth wouldn’t change, and the trace would stay at the same vertical position.

In M-mode, time is plotted along the horizontal axis and depth (distance from the transducer) along the vertical axis, so you’re watching how far away a reflector is over time. If a reflector moves toward the transducer, its depth decreases and the echo trace moves upward on the screen; if it moves away, the depth increases and the trace moves downward. Therefore, a line that moves up and down shows the reflector is moving along the beam axis—closer to and farther from the transducer. If the object moved only laterally, its depth wouldn’t change, and the trace would stay at the same vertical position.