A point, line, or surface of a vibrating body marked by absolute or relative freedom from vibratory motion is referred to as?

• A. A node
• B. An antinode
• C. Rarefaction
• D. Compression

Answer: (A)

In vibrating systems, a point, line, or surface that shows zero vibratory motion is called a node. This occurs in standing wave patterns when the two interfering waves cancel motion at that location, so displacement is zero even though other parts of the body vibrate. An antinode, by contrast, is where the motion is at its maximum. The terms rarefaction and compression describe regions of low and high pressure or density in a longitudinal wave, not locations of zero motion. Understanding nodes helps in visualizing standing waves and resonance in ultrasonic test setups, where specific patterns of motion affect how energy is transmitted and detected.