What are Electromagnetic Waves?

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A. Electromagnetic Waves. Definition

While it sounds somewhat psychedelic, an electromagnetic wave (EMW) is, in the workings of physics, defined as a wave produced by the interaction of time-alternating electric and magnetic fields.

Both electricity (your hair sticking straight up) and magnetism (a refrigerator magnet) can be static. However, when the two change or come together, they form a specific type of wave known as an electromagnetic wave.

Electromagnetic waves form when an electric field merges with a magnetic field. In directional form, magnetic and electric fields of an electromagnetic wave are perpendicular to one another and to the direction of the wave.

Commonly found examples of electromagnetic waves include: light, microwaves, x-rays, and TV and radio transmissions. All of these forms possess a similar, wave-like disturbance that systematically repeats itself over a distance known as a wavelength.

B. Electric Force Fields and Charged Particles

The wave, or disturbance, is in an invisible thing called the electric force field. To understand electric forces, we first need to understand the basic working components, charged particles, electrons, and protons. Without charged particles, there would be neither electric force fields nor electromagnetic waves.

The electric force field works along the lines of an invisible spring. However, as the charges move farther apart, a weaker spring continues to pull them together.

Rather than being dependent upon velocity (speed or power of the pulling), the force is solely hinged upon its positioning. Different in nature, an electron's motion is contingent upon both the force pushing on the electron and its velocity (often in different directions).

Note: James Clerk Maxwell and Heinrich Hertz are two scientists who studied the formation of electromagnetic waves and the speed at which they travel.

C. Electric Force Fields and Lines of Force

In physics, a force field represents a method for visualizing the effects that electrical charges have on one another. Rather than discussing the force that a positive (+) charge exerts on an electron, we can assume that the charge creates a force field in the empty space around it.

Any electron dropped down (regardless of its location in the force field) will automatically be pulled toward the + charge; whereas a + charge set down at the same place will be pushed away from the line of force.

An overview of how lines of force operate can best be conceptualized by looking at the charges of energy produced by the field in numerous locations. Next, imagine that there is a line that connects all of the electrons.

The lines derived are what are known as lines of force. Essentially, they are force field lines both coming and going in and out of the big + and big - charges. In this formation, the two charges are connected to one another by field lines.

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D. Wavelength
Wavelength is the distance between identical points in the adjacent cycles of a waveform signal. Wavelength is inversely related to frequency. The higher the frequency of the signal is, the shorter its wavelength. If "f" is the frequency of the signal as measured in megahertz (and "?" is the wavelength as measured in meters, then the following is true:
?= 300/f

And conversely,
f = 300/?

Note: Sometimes, wavelength is represented by the Greek letter, Lambda, which takes the form ?.
E. The Electromagnetic Spectrum and its Waves
of Many Different Types

Electromagnetic waves have different wavelengths. In the electromagnetic spectrum, waves vary in size from very long radio waves, the size of skyscraper buildings, to very short gamma rays, smaller than the size of the nucleus of an atom.

The electromagnetic spectrum includes, in order from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma rays. Plus, the electromagnetic spectrum includes all wavelengths in between the polar extremes.

Not only can electromagnetic waves be described by their wavelength, but they can also be characterized and categorized according to their levels of energy and frequency.

All three of these measurement traits are related to one another in a mathematical sense, and it is acceptable to use all of them regardless of the type of wave in question, for instance, energy of an X-ray, wavelength of a radio wave, or the frequency of a microwave.

Radio waves have the longest wavelengths in the electromagnetic spectrum. While they can indeed be as long as a football field, they can also be as short as a football. Radio waves function to transmit not only music, DJs and on-air talk shows to your radio; they also transmit signals for your television and cellular phones.

Microwaves

The wavelengths of microwaves can be measured in centimeters. Longer microwaves (approximately a foot in length) are the waves we use to heat our food in a microwave oven. Because microwave energy can penetrate haze, light rain, and snow, clouds, and smoke, microwaves serve as an effective and non-conditional means of transmitting information from one place to another.

Infrared Light

Infrared light exists between the visible and microwave portions of the electromagnetic spectrum. Just as visible light has wavelengths ranging in vibrant colors from red light to violet, infrared light has a range of wavelengths. For example, near infrared light is closest in wavelength to visible light whereas far infrared is closer in to the microwave range of the electromagnetic spectrum.

Far infrared waves possess thermal (heat-like) qualities. The heat that we feel from sunlight, fire, a radiator, or a warm patch of the pavement is derived from infrared rays. Interestingly enough, the shorter, near-infrared waves, such as those used in television remote controls, possess no thermal-like qualities; you can't even sense their presence when they are near.

Visible Light Waves

The only electromagnetic waves we can see with the naked eye are those of visible light waves. These are the ones which create the colors (red, orange, yellow, green, blue, and violet) of the rainbow.

Each color has a different wavelength. Red, which appears in the outermost shell of the rainbow, has the longest wavelength; violet, contained within the smallest, inner shell, has the shortest wavelength. When all of the visible light waves are seen together, they cancel out each other and appear as white light.

Ultraviolet Lights

Ultraviolet (UV) light has shorter wavelengths than visible light, and while UV waves are invisible to the human eye, some insects, like bumblebees, are able to detect them.

Ultraviolet lights have been divided by scientists and physicists into the following three ranges: near ultraviolet, far ultraviolet, and extreme ultraviolet. Overall, the three ranges are generally characterized by the amount of energy given off, and the wavelength of the ultraviolet light. Both of these traits are energy-related.

X-Rays

As the wavelengths of light decrease, the waves increase in energy. X-rays adhere to this rule, and have smaller wavelengths but higher energy than ultraviolet waves.

X-rays are characterized by their energy (which is more plentiful) instead of by their wavelength.

Gamma Rays

Compared to the other waves in the electromagnetic spectrum, gamma rays have the smallest wavelengths, but the greatest amounts of energy.

Generated by radioactive atoms and in nuclear explosions, gamma rays can kill living cells. This scientifically known fact has been applied to medicinal uses and has been effectively used to kill cancerous cells.

Though gamma rays reach us only after traveling across vast distances of the universe, ultimately they are absorbed by the Earth's atmosphere.

F. Wave Activity

The wave component consists of a wiggling line of electric force attached to the vibrating charge. If you observe a wave for a given period of time, you are certain to notice that it takes a fair amount of time for the wave to move from one particle to the other. As you increase the frequency by wiggling it up and down faster, you will find the distance between peaks (wavelength) decreases. This is because the faster the frequency, the more waves that are produced, thus the shorter the synapse (gap) between peaks.