From Television to X Ray: All About Electromagnetic Waves

What Are Electromagnetic Waves?

Electromagnetic waves or radiation is just another term for light. In particular, this term refers to the variations of electric and magnetic fields in space. Electromagnetic waves are produced when an electric field combines with a magnetic field. Electromagnetic radiation can be detected through a light detector. A good example of a light detector is your eye, which has the ability to detect white visible light containing all the rainbow colors from red to violet. But some light are not visible to our human eye. To detect this kind of radiation, we need special detectors. Such detectors include cell phones, radios, televisions, computers and x-ray machines. You might not know it, but you are actually using electromagnetic waves when you watch TV, cook in a microwave oven or listen to the radio.

The Discovery of Electromagnetic Waves

In the 19th century, James Clerk Maxwell, an English Scientist, discovered that the combination of electrical fields and magnetic fields could form electromagnetic waves. Both electricity and magnetism can be static, but Maxwell discovered that when these fields change or move together they form waves. This led to Maxwell’s scientific theory on electromagnetic waves.

When Maxwell studied the speed of electromagnetic waves, he discovered that it was nearly equal the speed of light. He interpreted this to mean that light was just another kind of electromagnetic wave. He further concluded that there also existed electromagnetic waves of other wavelengths. This electromagnetic theory of Maxwell would later be confirmed by a German physicist named Heinrich Hertz who produced the first man-made radio waves in 1887 (eight years after Maxwell’s death). Radio waves have longer wavelengths than visible light.

Maxwell’s Equation

Four basic laws, collectively known as Maxwell’s equation, govern the behavior of electric and magnetic fields. We now know that particles with an electric charge are subject to the forces acting upon them by the electric and magnetic fields. However, the source of the total electric field is the electric charges in the particles and the source of the total magnetic field is the motion of the charged particles that produces electric current. Therefore these charged particles are continuously interacting with one another through the electric and magnetic fields which they create. Maxwell’s equations make it possible for us to study electromagnetic phenomena which range from waves, like the light waves in a vacuum, to the solar wind’s effect on a planetary magnetosphere.

The Electromagnetic Spectrum

Electromagnetic (EM) spectrum refers to the various types of radiation. Two common examples of electromagnetic radiation are the light that you see from your lamp and the radio waves from a radio station. Microwaves, X-rays and gamma-rays, and infrared and ultraviolet light are other examples of EM radiation. Objects and events that are hotter and more energetic normally create higher energy radiation as compared to cool objects.

X-rays and gamma rays are examples of high energy radiation produced by exceedingly hot objects or particles that travel at very high velocities. We may think that because radio waves and Gamma rays are produced and detected in very different ways they are two different things. In fact, radio waves and Gamma rays are basically the same thing. Like visible light, x-rays and all other parts of the electromagnetic spectrum are all electromagnetic radiation.

All electromagnetic radiation has photons which have a certain amount of energy. The different amount of energy found in these photons is what spells the difference between the different kinds of electromagnetic radiation. Radio waves have photons with the lowest amount of energy. Microwaves, with a little more energy come next to radio waves. Following microwaves are infrared, visible, ultraviolet, X-rays, and finally gamma-rays, which are the most energetic of all.

Energy, Wavelength or Frequency?

The electromagnetic spectrum can be described by their wavelength, energy or frequency. All three of these ways of thinking about the EM spectrum are mathematically related to each other. This only means that it doesn’t matter if you talk about the wavelength of a microwave or the energy of an X-ray or the frequency of a radio wave. The electromagnetic spectrum from the longest wavelength to the shortest includes: radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma-rays.