Electromagnetic waves are simultaneous periodic oscillations in the intensity of an electromagnetic field. Unlike traditional waves, they do not need a medium to travel through, and they travel at the speed of light. There are seven types of electromagnetic waves: radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.
The term "electromagnetic" simply means "related to electromagnetism." Electromagnetism refers to the two overlapping worlds of magnetism and electricity in the scientific context. Although electricity and magnetism were discovered independently, electromagnetism is now considered the fundamental physical force that explains reactions between charged particles (protons and electrons) and the release of photons (electromagnetic waves).
The first scientist to bridge the gap between electricity and magnetism was Gian Romagnosi. In 1802, he discovered that running an electric current through a battery would disturb a nearby compass needle. But it wasn't until James Clerk Maxwell, a few decades later, that electricity and magnetism were unified in a single theory. The worlds of magnetism, charged particles, protons, electrons, and electricity were finally brought together.
However, Maxwell's theories were not compatible with classical mechanics, including Newton's laws. And it wasn't until Albert Einstein's 1905 paper on special relativity that this incompatibility was fully explained. Today, we consider electricity (the flow of electrons) and magnetism (the interactions between protons, electrons, and light) to be two sides of the same coin.
There are many terms related to electromagnetism, most of which have origins in the physics of physical waves, as one might find in the ocean. The following is a brief definition of six very important terms related to the structure of waves.
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Electromagnetic waves are not invisible. Our eyes can detect them, of course. Visible light is simply one of the seven types of electromagnetic waves, the type our eyeballs can detect. Across the electromagnetic spectrum there are six other types as well. But unlike with physical waves that one might find in a pond or in the ocean, the structure of electromagnetic waves in invisible. To help imagine the shape of such waves, scientists use diagrams like the one below.
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Electromagnetic waves can be visualized as pictured, with a simultaneous oscillation of the strength of both the electric and the magnetic fields. Thus, the two waves shown can be thought of as one wave with both a vertical component (electric) and horizontal component (magnetic).
The frequency of the wave would be a measure of how many times it completes a cycle in each second. The frequency of electromagnetic waves is very high, completing millions upon millions of cycles each second. The wavelength of the wave could be measured by taking a ruler (in this case, a very tiny ruler) and measuring the waves from crest to crest or trough to trough. The wavelength of electromagnetic waves are tiny, usually measured in nanometers. Finally, by measuring the frequency and wavelength, we could determine where this wave falls in the electromagnetic spectrum. It could be visible light, or a radio wave, or even an X-ray, depending on its wavelength and frequency. For more information on the types of electromagnetic waves, read the section below.
There are seven types of electromagnetic waves, all of which are similar periodic oscillations in the electromagnetic field. Scientists simply classify the waves based on their frequency and wavelength (which go hand in hand). Put together, one ends up with a diagram of the entire electromagnetic spectrum, as can be seen in the image.
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The seven types of electromagnetic waves can be thought of as seven different kinds of light. There is only one kind that our eyeballs can detect. However, it is important to note that this is a very human distinction. Some snakes can see infrared light. Some birds can detect ultraviolet light. All in all, these seven types of waves are fundamentally the same. The only difference is their frequency and, ultimately, their effects.
Radio waves are low-frequency, long-wavelength electromagnetic waves. They are the least energetic type of electromagnetic wave. Their wavelength is defined as any wavelength above 1 millimeter, and their frequency is defined as any frequency below 300,000,000,000 Hertz.
Microwaves have a higher frequency and shorter wavelength than radio waves. Their wavelength is defined as any wavelength between 1 millimeter and 25 micrometers, and their frequency is defined as any frequency between 300,000,000,000 and 10,000,000,000,000 Hertz.
Just above microwaves, with a slightly higher frequency and slightly shorter wavelength, is a type of light called infrared light. Infrared wavelengths are defined as any wavelength between 25 micrometers and 2.5 micrometers, and their frequency is defined as any frequency between 10,000,000,000,000 and 400,000,000,000,000 Hertz.
Just above infrared light is visible light. It is not fundamentally different from infrared, but it has a high enough frequency that it can be detected by the human eye. It comes in a variety of colors (red, orange, yellow, green, blue, purple, etc.) that all correspond to different frequencies. The wavelength for visible light varies from 400 to 750 nanometers, and the frequencies are between 400,000,000,000,000 and 750,000,000,000,000 Hertz.
Beyond visible light, with just a slightly higher frequency, is ultraviolet light. Ultraviolet light cannot be detected by the human eye, but it is absorbed by the human skin and used in the production of Vitamin-D. The wavelengths for ultraviolet light vary from 1 to 400 nanometers, and the frequencies are between 1,000,000,000,000,000 and 100,000,000,000,000,000 Hertz.
Beyond ultraviolet light are x-rays. They have a higher frequency, carry more energy, and have shorter wavelengths. They can also be dangerous, capable of damaging human cells and causing cancer. The wavelengths for X-rays range from 1 nanometer to 1 picometer, and the frequencies are between 100,000,000,000,000,000 and 100,000,000,000,000,000,000 Hertz.
Gamma rays are the highest-frequency type of electromagnetic radiation. They are also the most dangerous. They have a very small wavelength, a high frequency, and each photon carries a huge amount of energy. Gamma rays can be very harmful to humans in high amounts. The wavelengths for gamma rays are classified as anything less than 1 picometer, and the frequencies are anything above 100,000,000,000,000,000,000 Hertz.
Electromagnetic waves are periodic oscillations in the intensity of an electromagnetic field. They come in seven types: radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. One can think of them as seven different kinds of light. And although only one is detectable by the human eye, they are involved in everything from the production of Vitamin-D (ultraviolet light) to the sending of signals over Bluetooth (radio waves).
Discoveries in modern physics have illuminated the fact that electricity and magnetism are simply two sides of the same coin. Electricity is the flow of charged particles called electrons, Magnetism is the interaction between charged particles (electrons and protons). Electromagnetic waves are simply changes in the arrangements of charged particles, which have a wave of reverberating through space and time. Electromagnetic waves are studied using some of the same terminology as physical waves (wavelength, frequency, amplitude, crest, trough, cycle, etc.). They are also categorized by their frequency and wavelength into the seven types mentioned above.
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The seven types of electromagnetic waves are radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. The preceding list is in order from lowest frequency and least energetic (radio waves) to highest frequency and most energetic (gamma rays).
Electromagnetic waves are not mechanical waves. They do not travel through a medium and they do not have mass. They do carry energy, however.
Electromagnetic waves are simultaneous periodic oscillations in the intensity of an electromagnetic field. One probably knows them better as "light."
Electromagnetic fields are indeed transverse waves. This means that they travel in a direction perpendicular to their direction of oscillation.
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