# Electromagnetic Waves: History, Properties, Sources, and Types

Electromagnetic waves – Have you ever heard a song or broadcast sound that appears on the radio. So, do you know that live broadcasts and songs that appear on the radio that we can listen to everyday are examples of the application of electromagnetic waves, you know .

In general, waves are divided into two, namely electromagnetic waves and mechanical waves. Mechanical waves can propagate through an intermediary or medium. Mechanical waves can be transverse waves such as the process of propagating on a rope and can also propagate as longitudinal waves such as sound through the medium of air or other objects.

Meanwhile, electromagnetic waves are waves that can propagate even though there is no medium or intermediary. Electromagnetic energy can propagate in the form of waves with several measurable variables.

## Definition of Electromagnetic Waves

The first thing we will discuss together is the notion of electromagnetic waves, which are waves that have a charge of electric and magnetic energy and do not require a propagation medium.

That means these waves can propagate even though they are in a vacuum. Electromagnetic waves have a shape like a transverse wave in general, which has a direction of propagation that is perpendicular to the direction of vibration.

In everyday life, humans have used a lot of electromagnetic waves, such as the example mentioned at the beginning of the paragraph. As previously explained, electromagnetic waves in the form of waves have several variables that can be measured.

Some of these variables are wavelength, frequency and speed. Wavelength is the distance between the two peaks. As for the frequency itself is the number of waves that pass a point in one unit of time.
When viewed mathematically is as follows.

C = λ.f
Description:
C = speed of light
Λ = wavelength
F = frequency

It should be noted that the electromagnetic energy emitted or released by all masses in the universe has different levels. The higher the energy level possessed by an energy source, the lower the wavelength of the energy that is successfully produced as well as the higher the frequency.

## A Brief History of Electromagnetic Waves

After understanding what it means. We will learn together about the brief history of the existence of electromagnetic waves.

Before the 19th century, humans could only perceive visible light. Apart from visible light, of course, humans at that time did not know any other light.

Over time, until after 1800, there was an English astronomer born in Germany named William Herschel who had a discovery that stated that there was light or light other than visible light.

This discovery made by Herschel could be the beginning of the development of electromagnetic wave matter. Of course, the discoveries made by Herschel will continue to be developed by other scientists.

In the past, Herschel conducted an experiment using a prism to diffract sunlight. At that time he managed to find a light that is invisible to the human sense of sight outside the red area which can cause the thermometer to get hot or high. Then the rays are named infrared rays or infrared.

After a year from the Herschel meeting, another discovery emerged from the German physicist named Johann Wilhelm Ritter whose discovery was a beam of light that was close to purple and remained invisible to the human sense of sight.

Experiments conducted by Ritter at that time used a prism to diffract sunlight. The light found can cause silver chloride plates to turn black. Until then the color rays are given the color of ultraviolet light.

Then at the end of the 19th century, a German physicist named Wilhelm Rontgen discovered a beam of light that could penetrate a solid object and was given the name X-rays or X-rays.

The next few years were preceded by the discovery of alpha and beta rays by Rutherford, a French physicist and chemist named Paul Ulrich Villard discovered a third beam of light from experiments conducted by Rutherford.

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These rays have neutral properties and have a higher energy than X-rays. Where the discovery of these rays is named gamma rays. Among the others, gamma rays have the highest frequency in electromagnetic waves.

In 1862 to 1864, James Clerk Maxwell undertook the development of a theory closely related to electric fields and magnetic fields. He has an opinion that a change in the electric field can cause a change in the magnetic field, so that a wave can be created.

After 25 years of the experiment then proved by Heinrich Hertz. Hertz discovered a wave outside the range of infrared light, which is then called microwave and radio.

From the experiments conducted by Hertz, Maxwell’s theory was finally proven and justified. And Maxwell’s discovery was named electromagnetic waves or GEM.

Then in 1905, Albert Einstein discovered a concept of special relativity which could eventually perfect the concept of electromagnetic waves.

## Properties of Electromagnetic Waves

Electromagnetic waves also have some properties in them. So that you can more easily understand electromagnetic waves. Here are some of the properties possessed by electromagnetic waves.

1. Changes in the electric field and magnetic field in electromagnetic waves will occur simultaneously.
2. Can propagate in a vacuum.
3. The magnitude of the electric field (E) is directly proportional to the magnitude of the magnetic field, with the relationship E = cb.
4. The directions of the electric and magnetic fields are perpendicular to the direction of the wave propagation.
5. This is a transverse wave.
6. Can experience polarization, reflection events (reflection), refraction (refraction), interference, and bending (diffraction).
7. Have momentum.
8. Can be divided into several types depending on the frequency or wavelength.
9. The speed of propagation of electromagnetic waves in a vacuum is a general constant (constant) c = 3 x 108 m/s. (meters/second = meters/second).

Those are some of the properties possessed by electromagnetic waves.

## Source of Electromagnetic Waves

The existence of electromagnetic waves can also occur from several sources. The following are some sources that can produce electromagnetic waves.

1. Electrical Oscillation
2. Sunlight
3. Infrared lamps that can specifically produce infrared
4. Ultraviolet lamp which can specifically produce ultra violet
5. Electron shooting in a vacuum tube on a metal chip can produce X-rays or commonly referred to as X-rays.
6. Unstable atomic nuclei are capable of producing alpha, beta, and gamma radiation. And for gamma radiation is one of the electromagnetic waves.

### Electromagnetic Wave Spectrum

Electromagnetic waves include light, radio waves, X-rays, gamma rays, microwaves and others. The various forms of electromagnetic waves are distinguished only by their wavelength and frequency.

## Types of Electromagnetic Waves

Electromagnetic waves can also be divided into several types. If you don’t know what types of electromagnetic waves are, then the explanation below can help.

Radio waves are a type of electromagnetic wave. Where there are electromagnetic waves is when sound or audio turns into an electrical signal by going through an oscillator wave or carrier wave.

Or simply radio waves can be generated by electric charges accelerated through a conductor wire. This charge will be generated by an electronic circuit called an oscillator. Raido waves will be emitted and received by the antenna.

Some objects that use radio waves are like television, radio, telephone and radar. Electromagnetic waves were first discovered by Heinrich Hertz and used by Marconi as a medium of communication.

### 2. Microwave or Microwave

Microwaves or microwaves can be generated by klystron tubes which have a function as a conductor of heat energy. The frequency of electromagnetic waves in microwaves is quite high, which is around 3 GHz (3×109 Hz).

If microwaves are absorbed by an object, molecule or atom, the object will vibrate causing a heating effect. Then if there is food that absorbs microwave radiation, then the food can heat up and cook in a relatively short time. This process is used in microwave ovens.

Microwaves can also be used in radar or Radio Detection and Ranging. Radar can be used to search for and determine traces of an object by utilizing microwaves.

### 3. Infrared waves or Infra Red

Infrared is an electromagnetic wave with a longer wavelength than visible light. Even so it turns out that infrared wavelengths are shorter than radio waves.

The long range of infrared wavelengths ranges from 1000 nm to 1 mm. Infrared light is produced by electrons present in vibrating molecules and will likely break up into different parts of the molecule as the object is heated. The energy released by these vibrating atoms and molecules is in the form of infrared radiation.

It should also be noted that every hot object must have emitted infrared waves. Currently, infrared waves are already widely used in objects in everyday life such as TV remotes, data transfer from cell phone to other cell phones to physical therapy.

### 4. Visible Light

As the name suggests, visible waves can indeed be seen directly by the human sense of sight. Visible waves consist of seven colors. Where if sorted from the greatest frequency, starting from red, orange, yellow, green, blue, indigo, and purple.

As for the wavelength of each light is as follows.

• Red has a wavelength between 620 and 780 nm.
• Orange has a wavelength between 590 and 620 nm
• Yellow has a wavelength between 570 to 590 nm
• Green has a wavelength between 490 to 570 nm
• Blue has a wavelength between 450 to 490 nm
• Indigo has a wavelength between 420 to 450 nm
• Purple has a wavelength between 380 to 420 nm

Just for information 1 nm = 1 nano meter = 10-9 meters.

As additional information, 1 nm is 1 nano meter, which ranges from 10 to 9 meters. Then for visible light waves until now it has also been used in a number of objects such as internal lasers and optics in the fields of telecommunications and medicine.

### 5. Ultraviolet Rays

The sun is the main source of light that can emit ultraviolet light to the earth’s surface. Ultraviolet light can also be produced by electron transitions in atomic orbits, carbon arcs and mercury lamps .

Ultraviolet light is actually part of the color spectrum. However, the human sense of sight is incapable of seeing ultraviolet light. In addition, ultraviolet light also has a very short wavelength when compared to other colors.

This is because ultraviolet light has a stronger penetrating power than other colors of light. Even ultraviolet light or ultra violet light is also able to penetrate human skin and is able to change the structure of human skin cells.

At low levels, ultraviolet rays can provide assistance in the process of forming vitamin D. However, at high levels, ultraviolet rays can cause skin cancer.

It should also be noted that ultraviolet light is at a wavelength between 3 nm and 380 nm. Currently, the existence of ultraviolet light is widely used for UV lamps and for LASIK eye surgery.

### 6. Shinar X

Next there are X-rays which have very high penetrating power. Even bigger than ultraviolet rays. The wavelength of X-rays is quite short, but has such a high frequency.

Because it has an ordinary wide penetrating power, X-rays can penetrate soft structures such as meat and wood, thick books to aluminum plates as thick as 1 cm. But X-rays cannot penetrate solid structures such as bone.

With the ability of X-rays to penetrate flesh, it is not surprising that X-rays are often used for X-ray technology that can reveal bone or skeletal structures on film screens. X-rays are even used to track or view the contents of passenger bags at the airport.

The wavelength of X-rays ranges from 0.3 nm to 3 nm. Then the discoverer of X-rays was Wilhelm Rontgen (1823-1923) when he conducted high-voltage electron scattering experiments.

### 7. Gamma Rays

Gamma-ray waves can be written as Y-rays. Where gamma-ray waves can be called the strongest electromagnetic waves among other electromagnetic waves.

The wavelength of gamma rays ranges from 0.0003 to 0.03 nm or can also be written as 0.3 pm to 30 pm. Where 1 poko meter (pm) is 10 to 12 meters.

Gamma-ray waves are produced from radioactive decay events or unstable atomic nuclei. Gamma rays can also penetrate solid structures such as atomic structures into different atoms.

Even gamma rays also occur in a nuclear reaction process so as to produce a radiation that tends to be so harmful to living things. In the medical world, the existence of gamma rays is used to sterilize medical equipment and radiotherapy processes in the treatment of cancer.

Those are some types of electromagnetic waves that still exist today.