Properties and Applications of Electromagnetic Waves

All charge carriers that are accelerated or decelerated emit electromagnetic fields that spread through space. The strengths of the electric and magnetic fields change periodically both in space and time and therefore have the properties of waves. They are called electromagnetic waves.

All charge carriers that are accelerated or decelerated emit electromagnetic fields that spread through space. The strengths of the electric and magnetic fields change periodically both in space and time and therefore have the properties of waves. They are called electromagnetic waves .

Generation of electromagnetic waves

A dipole (e.g. long straight wire) in which the direction of current flow is periodically changed can be the starting point for electromagnetic waves. When the direction of the current changes, the charge carriers in the conductor wire are accelerated. The creation of the electromagnetic wave can be understood in the following way:

A periodically changing current flows in the dipole. When the current strength is at its greatest, a circular magnetic field builds up around the dipole , the orientation of which is determined by the direction of the current. During a complete oscillation, the flow of current comes to a complete standstill twice. Then the charge carriers are concentrated at the ends of the dipole. Electric field lines emanate from the positive end of the dipole and run to the negatively charged end of the dipole.

After polarity reversal, the dipole ends discharge and the electric field becomes weaker, while at the same time, a magnetic field builds up again around the conductor wire. During this process, the build-up and breakdown of electric and magnetic fields constantly alternate. A periodic alternating electromagnetic field is created. This field can detach from the surface of the dipole. Once released, it spreads through space at the speed of light. An electromagnetic wave was created.

In addition to the processes at the dipole, there are many processes in nature and technology in which charge carriers are accelerated or decelerated. This happens, for example, when very fast electrons in a vacuum electron tube collide with the anode and are suddenly stopped. This produces very short-wave electromagnetic radiation, called X-rays.

Many molecules have an uneven internal charge distribution of the electrons in the shell of the molecular structure. If these molecules rotate or oscillate, the charge carriers carry out an accelerated movement (e.g. radial acceleration of the circular movement) and therefore emit electromagnetic radiation. This radiation has a longer wavelength than X-rays and can be detected, for example, in the visible range of the electromagnetic spectrum or in the infrared range.

Large-scale flows of charged particles on the surface of the sun are the source of radio waves.

If the human senses were equally sensitive to all wavelengths of electromagnetic radiation, then we would have to perceive a veritable storm of signals and noise from a wide variety of electromagnetic waves. However, we can only register the visible part of the electromagnetic radiation with our eyes and are thus spared from the confusing multitude of incoming waves.

Properties of electromagnetic waves

Electromagnetic waves have many properties that can be determined regardless of their wavelength. These properties are primarily those that apply to any type of wave and are therefore often referred to as characteristic features of waves. These include reflection, refraction, diffraction, and interference .

These four characteristics can be demonstrated through experiments on all types of electromagnetic waves. However, the examination methods used differ depending on the wavelength of the radiation examined. While interference and diffraction phenomena in Hertzian waves have to be measured over a large area with a receiver, the mutual extinction and amplification of light waves are observed using special line gratings on a collecting screen.

To detect X-ray diffraction and interference, the radiation is passed through crystals whose atoms act as diffraction points.

By using polarizers, electromagnetic waves can also be polarized. With polarized waves, the electric field strength oscillates only in a given direction.