Characteristics of Waves

gmaktub (57)in #science • 8 years ago

Characteristics of Waves.

You just learned that there are many different kinds of waves. Sound waves, light waves, X-rays, microwaves, and ocean waves are but a few examples. All waves, however, share certain basic characteristics. All waves have amplitude, wavelength, and frequency.

In order to understand these characteristics of waves, it may help you to represent a wave as a drawing on a graph. The X-axis (the horizontal line) represents the normal, or resting, position of the medium, or field, before it is disturbed by a wave. For example, the X-axis might represent a calm sea or a tight rope. The vibrational movements of the wave are shown on the Y-axis (the vertical line). The highest points on the graph are called peaks or crests. The lowest points are called troughs).

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Amplitude.

If the wave disturbs a medium, the particles of the medium are moved from their normal (resting) positions. The distance the particles are moved from their resting positions is shown by the up and down pattern of the graph. Similarly, if the wave disturbs electric or magnetic fields, the graph shows the rise and fall of the fields. In any wave, the amount of movement from rest is shown by the distance above or below the X-axis. The maximum (or greatest) movement from rest is called the amplitude (AM-pluh-tood) of the wave. The amplitude can be found by measuring the distance from rest to a crest or from rest to a trough.

The amplitude of a wave indicates the amount of energy carried by the wave. As energy increases, particles of the medium are moved a greater distance from rest. Thus the amplitude of the wave also increases. The amplitude decreases as the wave loses energy.

Wavelength.

The distance between two consecutive (one after another) crests or troughs of a wave is called the wavelength. Actually, the wavelength can be measured from any point on a wave as long as it is measured to the same point on the next wave. Wavelength is usually measured in meters or centimeters. The symbol for wavelength is the Greek letter lambda (λ).

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Frequency.

The number of complete waves, or complete cycles, per unit of time is called the frequency). Because every complete wave has one crest and one trough, you can think of the frequency as the number of crests or troughs produced per unit time. The unit used to measure wave frequency is called the hertz (Hz). This unit is named after Heinrich Hertz, who was one of the first scientists to study certain types of waves. A frequency of one hertz is equal to one wave, or cycle, per second:

1 Hz = 1 wave / sec.

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The frequency of a wave depends on the frequency at which its source is vibrating. Think about the rope again. If you move your hand slowly, the rope vibrates slowly. Perhaps you will create one new wave every two or three seconds. If you move your hand rapidly, the rope vibrates rapidly. This way, you may create several waves each second. Try it and see.

Frequency, which is often used to describe waves, is an important characteristic. Frequency is used to distinguish one color of light from another, as well as one sound from another. For example, red light is different from blue light because red light has a lower frequency. A dog can hear a whistle that you cannot hear because dogs can hear sounds at higher frequencies than humans can.