What Are Electromagnetic Waves (and Their Characteristics)

Electromagnetic waves are the combination of waves in electric and magnetic fields produced by moving charges. That is, what ripples in electromagnetic waves are electric and magnetic fields.

The creation of electromagnetic waves starts with a charged particle. This particle creates an electric field that exerts a force on other particles. As the particle accelerates, it oscillates in its electric field, which produces a magnetic field. Once in motion, the electric and magnetic fields created by the charged particle are self-perpetuating, meaning that an electric field that oscillates as a function of time will produce a magnetic field and vice versa.

Characteristics of electromagnetic waves

Electromagnetic waves are characterized by:

  • They do not need a material medium for propagation: they propagate in material mediums and in a vacuum.
  • They result from electromagnetic signals.
  • They are transverse waves: the direction of propagation is perpendicular to the direction of oscillation.
  • They are periodic in time and space: oscillations are repeated at equal time intervals.
  • In a vacuum, the propagation speed of electromagnetic waves of any frequency is 3 x 108 m/s
  • Wavelength is the distance between two adjacent peaks between waves, designated by the Greek letter lambda λ.
  • The frequency of a wave is the number of cycles for a given time, it is expressed in Hertz which means cycles per second.

Types of electromagnetic waves

Depending on the wavelength and frequency, electromagnetic waves are classified into different types.

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Radio waves

Radio waves are characterized by:

  • frequencies between 300 gigahertz (GHz) and 3 kilohertz (kHz);
  • wavelengths between 1 mm and 100 km;
  • speed of 300,000 km/s.

Artificial radio waves are used in satellite communications and telecommunications, in radio transmissions, in radar and navigation systems, and in computer networks.

AM radio waves used in commercial radio signals are in the frequency range between 540 and 1600 kHz. The abbreviation AM stands for “amplitude modulation”. FM radio waves, on the other hand, are in the frequency range of 88 to 108 megahertz (MHz), and the abbreviation FM stands for “frequency modulation.”

Radio waves can be generated naturally by lightning or other astronomical phenomena.

Microwave

Microwaves are electromagnetic waves that are characterized by:

  • frequencies between 300 MHz and 300 GHz;
  • wavelengths between 1 meter and 1 mm;
  • They travel in a vacuum at the speed of light.

The prefix “micro” indicates that these waves are shorter than radio waves. Microwaves are also used for television and telecommunications transmissions, in cordless phones, in walkie talkiesin microwave ovens, and in cell phones.

infrared waves

Infrared waves are electromagnetic waves that are characterized by:

  • frequencies between 300 GHz and 400 terahertz (THz);
  • wavelengths between 0.00074 and 1 mm.

Infrared waves can be classified in turn into:

  • far infrared: between 300 GHz t 30 THz (1 mm to 10 µm)
  • mid-infrared: between 30 and 120 THz (10 to 2.5 µm); Y
  • the near infrared: between 120 and 400 THz (2500 to 750 nm).

visible light

visible light spectrum electromagnetic wave

Light is an electromagnetic wave characterized by:

  • frequencies between 400 and 790 THz.
  • wavelengths between 390 and 750 nm.
  • speed of 300,000 km/s.
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Visible light is produced by the vibration and rotation of atoms and molecules, as well as by electronic transitions within them. Colors occur in a narrow band of wavelengths, namely:

  • violet: between 380 and 450 nm;
  • blue: between 450 and 495 nm;
  • green: between 495 and 570 nm;
  • yellow: between 570 and 590 nm;
  • orange: between 590 and 620 nm; Y
  • red: between 620 and 750 nm.

ultraviolet light (UV)

The electromagnetic wave of ultraviolet light is classified into;

  • Near UV: between 300 and 400 nm;
  • Medium UV: between 200 and 300 nm;
  • Far UV: between 200 and 122 nm; Y
  • Extreme UV: between 10 and 122 nm.

UV light can cause chemical reactions and fluorescence in many substances. The extreme UV, can cause ionization of the substances it passes through (ionizing radiation). This type of UV light is blocked by oxygen in the atmosphere and does not reach the Earth’s surface. UV light between 280 and 315 nm is blocked by the ozone layer, preventing the damage they can cause to living beings. Only 3% of UV light from the sun reaches Earth.

Although UV light is invisible to humans, we can feel its effects on our skin when we tan or burn from prolonged exposure to the sun’s rays. Other harmful effects of UV light are cancer, particularly skin cancer. However, humans and all living things that produce vitamin D require UV light in the 295-297nm range.

X-rays

X-rays are electromagnetic waves that are characterized by:

  • energy in the range of 100 eV to 100,000 eV;
  • frequencies in the range of 30 petahertz to 30 exahertz;
  • wavelengths between 0.01 and 10 nm.
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X-ray photons have enough energy to ionize atoms and break molecular bonds, making this type of radiation harmful to living things.

Gamma rays

The electromagnetic waves of gamma rays are characterized by:

  • energies above 100 keV;
  • frequencies greater than 1019 Hz;
  • wavelengths less than 10 picometers.

These are the waves with the highest energy, discovered by Paul Villard in 1900 while studying the effects of radiation emitted by radium. They are produced by radioactive materials.