What is Amplitude? - Definition & Frequency

What is Amplitude? - Definition & Frequency
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  • 0:05 What Is Amplitude?
  • 1:53 Frequency
  • 3:24 Lesson Summary
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Lesson Transcript
Instructor: Thomas Zesiger

Thomas has taught electronics and communications engineering, math, and physics and has a master's degree in electrical engineering.

Discover practical examples of waves and the significance of wave amplitude. Learn about the relationship between frequency and wavelength and how they relate to the amplitude of the wave.

What Is Amplitude?

Ripples in water, sound traveling in air, and coordinated vibrations of objects are examples of waves you have probably encountered in your life. A good way to visualize a wave is to insert the end of a pencil into a container of still water. The surface of the water is disturbed, producing ripples, or waves.

Electromagnetic waves, such as light, radio waves, microwaves, and x-rays, are special waves that do not require a medium for propagation. We cannot see or hear these waves, but they exist in nature and in many of the products we use every day.

Regardless of the kind, every wave has an amplitude. Amplitude is the maximum displacement of points on a wave, which you can think of as the degree or intensity of change. This maximum displacement is measured from the equilibrium position. The following picture shows a diagram of a sine wave. The diagram shows amplitude and wavelength, which is the distance between two successive like points on a wave. Wavelength is like the distance between two adjacent peaks or two adjacent valleys. Stated another way, wavelength is the time required to complete one full cycle of the wave.

The equilibrium position is the straight line represented by the x-axis. It represents the shape of the medium when there is no wave, or when the water is still and undisturbed in the case of ripples in water. This helps us see another way to state the definition of amplitude, which is the vertical distance from a peak to the equilibrium position or from the equilibrium position to a valley. Amplitude is used to describe the peak value of such quantities as the level of sound waves, and power and voltage in electrical and electronic systems.

Frequency

The frequency is the number of wave cycles passing a point per unit time. Stated another way, it is the number of oscillations per second in the wave. A higher frequency means a shorter wavelength, and a lower frequency means a longer wavelength.

Although wavelength and frequency are related, amplitude and frequency are independent features of a wave. Both parameters can be changed, but changing only one does not affect the other. Changing frequency does not alter the amplitude of the wave, and changing the amplitude does not alter the frequency. There is also no way to determine the amplitude of a wave from the frequency or to determine the frequency simply by knowing the amplitude of the wave. This is shown in the following:

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