Characteristics Of Waves Motion

The two types of wave motion, 
Transverse and Longitudinal, have many of the same characteristics, such as frequency, amplitude, and wavelength. 

Another important characteristic that these two types of wave motion share is VELOCITY. 

Definition:

Velocity of propagation is the rate at which the disturbance travels through the medium, or the velocity with which the crest of the wave moves along. The velocity of the wave depends both on the type of wave (light, sound, or radio) and type of medium (air, water, or metal). If longitudinal waves are plotted as a graph, they appear as transverse waves. This fact is illustrated in figure 

The frequency of a longitudinal wave, like that of a transverse wave, is the number of complete cycles the wave makes during a specific unit of time. The higher the frequency, the greater is the number of compression and expansions per unit of time.
In the two types of wave motion described in the preceding discussion, the following quantities are of interest:

• The PERIOD, which is the time (T) in which one complete vibratory cycle of events occurs,

• The FREQUENCY OF VIBRATION (f), which is the number of cycles taking place in one second, and

• The WAVELENGTH, which is the distance the disturbance travels during one period of vibration.

Now, consider the following concept. If a vibrating object makes a certain number of vibrations per second, then 1 second divided by the number of vibrations is equal to the period of time of 1 vibration. In other words, the period, or time, of 1 vibration is the reciprocal of the frequency; thus,

If you know the velocity of a wave, you can determine the wavelength by dividing the velocity by the frequency. As an equation:

When you use the above equation, be careful to express velocity and wavelength in the proper units of length.

For example, in the English system, if the velocity (expressed in feet per second) is divided by the frequency (expressed in cycles per second, or Hz), the wavelength is given in feet per cycle. If the metric system is used and the velocity (expressed in meters per second) is divided by the frequency (expressed in cycles per second), the wavelength is given in meters per cycle. Be sure to express both the wavelength and the frequency in the same units. (Feet per cycle and meters per cycle are normally abbreviated as feet or meters because one wavelength indicates one cycle.) Because this equation holds true for both transverse and longitudinal waves, it is used in the study of both electromagnetic waves and sound waves.

Consider the following example. Two cycles of a wave pass a fixed point every second, and the velocity of the wave train is 4 feet per second. What is the wavelength? The formula for determining wavelength is as follows: