Sound and Oscillation

Electromagnetic waves

Electromagnetic waves are distributed over a wide range of increasing frequencies called the electromagnetic spectrum.

Infrared waves can be observed in heat cameras like the one shown in the figure above.
Electromagnetic waves are oscillations of electric and magnetic fields that propagate in a vacuum at the speed of light . As they are phenomena of wave nature, electromagnetic waves can undergo reflection , refraction , interference , polarization and diffraction .

What are electromagnetic waves?

Electromagnetic waves arise when an electric field undergoes some periodic oscillation in its intensity , thus producing a magnetic field perpendicular to that electric field. The propagation of the electromagnetic wave occurs in the direction perpendicular to the plane formed by the magnetic field and the electric field. Furthermore, all electromagnetic waves are capable of traveling in a vacuum at the speed of light , about 300,000 kilometers per second . . Despite being treated as waves, the current knowledge of Physics also allows us to say that the electromagnetic field is formed by countless massless particles, called photons .

Electromagnetic waves are distributed in order of increasing energy over a wide range of frequencies called the electromagnetic spectrum . In this article, we present some interesting facts about the different types of waves present throughout the electromagnetic spectrum. Check out:

Curiosity 1 – Radio waves

Radio waves are the lowest energy waves in the entire electromagnetic spectrum. They are also those with the lowest frequency and the longest wavelengths, whose dimensions can vary from a few meters to tens of kilometers. Radio waves are invisible to our eyes. These waves can be produced by oscillating electrical currents formed in conductors, such as in television, cell phone and radio antennas.

This type of electromagnetic wave is widely used in the transmission of information, such as in television, radio , Wi-Fi, Bluetooth, etc.

Curiosity 2 – Infrared

Like radio waves, infrared waves are not visible to the naked eye. These are waves that carry less energy than visible light. Infrared waves are continuously emitted by all bodies that are at room temperature (about 300 K). This emission occurs as a result of the physical phenomenon of blackbody emission , that is, the transfer of heat in the form of electromagnetic waves related to the temperature of the body.

In this way, it is possible to see living beings in regions of total darkness. That’s how night vision devices work. Infrared capture also allows us to see thousands of stars in the night sky that would not be seen with the naked eye.

Devices such as remote controls make use of infrared waves to control electronic devices. This is precisely why they don’t work well when placed under a thick blanket: blankets are made to reflect heat, in the form of infrared waves, back to our bodies, keeping us warm during a cold night.

Visible light represents a small portion of the electromagnetic spectrum, more precisely between the wavelengths of 750 nanometers (nm) and 400 nm , and varies between blue and violet colorations. Electromagnetic waves of a wavelength immediately greater than red are called infrared, while electromagnetic waves of a wavelength immediately less than the wavelength of light colored violet are called ultraviolet.

The perception of colors can vary according to the individual, since the capture of light is done in the eyes by a set of cells called cones. Cones transmit information to the brain, which is translated into the perception we have at each wavelength.

Curiosity 4 – Ultraviolet

Ultraviolet light is largely produced by the Sun. It is a non-visible and ionizing radiation, since this type of electromagnetic wave is capable of producing changes in DNA chains, which can cause irreversible cell damage.

Some insects, such as bees, are able to see ultraviolet rays. This is because the flowers reflect a part of the rays coming from the Sun, making them easier to locate. In addition, some spiders are known to know this mechanism and produce webs capable of reflecting ultraviolet light, deceiving insects.

Curiosity 5 – X-Rays

X – rays are widely used in medicine for diagnostic imaging. X-ray is a high energy electromagnetic wave capable of being transmitted with little loss through soft tissues such as skin and muscle. This ray, however, is absorbed by the vast mineral content of bones. X-rays are also used in radiotherapy, aimed at fighting tumor cells, and in more complex exams, such as tomography.

Because they are highly energetic, X-rays are capable of producing changes in the DNA strands of cells, causing them to undergo genetic mutations that can induce cancer. That’s why exposure to this type of radiation should be limited.

Curiosity 6 – Gamma rays

Gamma rays are mainly emitted by radioisotopes that undergo nuclear decay. In these high-energy reactions, atomic nuclei disintegrate, producing other smaller and more stable nuclei and emitting extremely energetic electromagnetic waves with high penetration power: gamma rays .

Furthermore, unlike other types of electromagnetic waves, gamma rays are hardly reflected, as their wavelength allows them to be transmitted through the space between atoms.

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