A vibration graph displays the behavior at a SINGLE location along the wave's path as time passes. One vibration can be defined as one complete cycle, or back and forth motion.

 

 

The period of a periodic wave is defined as the amount of time required for a vibrating particle to return to its original observed position. The period can be calculated using the following equation:

 

 

When calculated, the unit of measure is usually expressed as just seconds (sec), instead of seconds per vibration. But either are considered to be correct.

 

The frequency of a periodic wave represents how many vibrations a particle makes in a given amount of time, usually one second. It can be defined as

 

 

When calculated, the unit of measure is usually expressed as hertz (hz), instead of vibrations per second. But either are considered to be correct.

 

As you can see from their respective definitions, period and frequency are reciprocals.

 

 

Remember that the amplitude of the graph is an indication of a mechanical wave's energy content; the greater the amplitude, the more energetic the source that produced the waves. We are now going to examine to vibration graphs in detail.