Sound and Oscillation

# Types of periodic waves

The waves which are produced by continuous and rhythmic disturbances in a medium are called periodic waves. These may be transverse or longitudinal in nature. A good example of periodic waves is an oscillating mass-spring system that executes Simple harmonic motion.

## Types of Periodic waves

• Transverse periodic waves
• Longitudinal periodic waves

### Transverse periodic waves

The periodic waves in which the displacement of particles of medium is perpendicular to the direction of motion of waves are called transverse periodic waves.
Experiment.
Let us consider a mass-spring system that can vibrate vertically. A long string of uniform thickness is stretched horizontally and its one end is attached with the oscillating mass m. Due to the oscillation of the mass-spring system a transverse wave is produced in the string.
The wave appears to be traveling on the spring, from one end to the other. In this case, each part of the string vibrates at the right angle to the length of a stretched string. The crest and troughs are being replaced by one another periodically and waves appear to be traveling.

### Longitudinal Periodic waves

The periodic waves in which particles of the medium vibrate along the direction of motion of waves are called longitudinal periodic waves or compressional periodic waves.
Experiment:
To explain longitudinal periodic waves, we take an example of a spring that is suspended with the help of threads. Longitudinal waves are produced in this string by applying horizontally varying force at one end of the spring. This force produces compressions and rarefaction in the spring.
In this case, the various parts of the spring vibrate along the length of the spring. When spring was undisturbed then all the suspension threads were vertical.
But when the longitudinal wave is produced in the string then these suspension threads are displaced. Their displacement is the same as the displacement of corresponding parts of the spring.
The graph of displacement of various parts of spring and corresponding values of the distances of these parts of spring, from its one end.
Also read: Transverse waves and Longitudinal waves