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Electromagnetic Waves


Electromagnetic waves or EM Waves are the waves that are created as a result of vibrations between a electric field and a magnetic field. In a vacuum EM waves travels at the speed of light, That is 3*108 ms-1. Also it does not require a medium to travel like mechanical waves such as sound waves and it can travel through almost anything.

EM waves are the synchronized oscillations of an electric field and a magnetic field and these oscillations are perpendicular to each other, also perpendicular to the direction of the wave propagation.

They are not something that has been created with the development of science. EM waves were always in the environment with the development of science they were identified. Light is electromagnetic wave. Even the sunlight.

History of Electromagnetic Waves

Science did not happened in over night. The first written document about electricity related phrases runs to 28th century BC, Which ancient Egyptians had written about an “electric fish”. After decades and centuries of observations and experiments William Herschel discovered infrared radiation from the sun in 1800. In 1801 ultraviolet radiation was discovered by Johann Ritter.

Read about the history of electromagnetism and optics

Electromagnetic Spectrum

The entire distribution of the EM radiation according to their wavelength or frequency is called the “Electromagnetic Spectrum”. The EM spectrum contains many sub ranges which are referred as portions. Each portion has their own name based on their behavior. There are no precise boundaries to these portions therefore the ranges tend to overlap.

The discovery of the infrared was the first discovery of the EM radiation other than light. He was studying the temperature of different colours using a moving thermometer through light split by a prism and noticed that the highest temperature was beyond the red. He presented his theory that this high difference of temperature is due to a type of light ray that could not be seen. Ritter experimented from the other end of the spectrum and discovered that there are rays that behave almost equally to the violet in the visible light which he named as “Chemical Rays”. This meant that invisible light induced certain chemical reactions.

The EM spectrum contains all the radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays.

Uses of EM Waves

Radio waves are used in the broadcasting by the radio and television companies.

Microwaves are used in transmitting information between earth and satellites, RADAR, microwave ovens.

Infrared

Since any object that radiate heat, uses infrared. So the infrared cameras can detect the objects in the dark. This is called “thermal imaging”. Police and Army uses these IR cameras. IR radiation is used in weather satellites.

Also IR is used in infrared tracking or infrared homing. IR tracking is a passive missile guiding system that tracks the target by detecting the IR emitted by the target.

The heating property is used in IR saunas and to remove the ice from the air crafts. Also using IR as a heating agent is efficient since IR radiation heat only the opaque objects. So if IR radiation is used to heat food it only heat the food not the air around the food. Which means almost all energy in IR is used to heat the object and does not waste.

Also IR radiation is popular among industrial manufacturing such as curing coats of paints, plastic manufacturing and IR is considered the best choice for light in standard silica optical fibers.

IR reflectography is using IR radiation to scan and identify the underlying paint layers in a painting while not damaging the painting in anyway.

Not only IR but also the visible light is used in fiber optic transmitting.

Ultraviolet

Ultraviolet or UV radiation is used in photography, Which are important in medical, scientific and forensic investigations. Because it can help to identify bruises on the skin, blood, semen or other bodily fluid, document forgery

Amusement parks often use UV lights fluorescent dies in artwork and backdrops because UV fluorescent die glows under UV lights creating a magical experience in the dark.

UV radiation is used in identifying illegible documents, such as the burnt papyrus of the Villa of the Papyri.

Hotels use UV radiation in identifying the missed spots during cleaning. Also other manufacturing where the cleanliness or contamination is inspected.

By FASTILY (TALK) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=12157782

UV spectroscopy is highly used in modern science to identify the compounds. Also UV lamps are used to identify minerals and gems.

Not only IR radiation but also the UV radiation is used to cure paint coatings. Specially the polymer paints. There are UV lamps for the curing.

Most air purifiers and water purifiers use UV radiation in the process of purifying.

Ultraviolet radiation is used in treating for skin conditions such as vitiligo.

X-Rays

The most famous use of the X-rays is the “Projectile Radio-graphs” or simply “X-ray”. Computed tomography or CT scan machines uses x-rays.

By daveynin from United States – New UPMC EastUploaded by crazypaco, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=20326407

Also x-rays are used in radiotherapy in curing cancer. Lower energy beams are used on skin cancers while high energy beams are used on cancers inside the body.

X- ray microscope helps to get magnified image of an object.

Also X-rays are used to identify the composition of a sample by running a x-ray beam within an unknown sample.

Not only x-ray imaging is used in medically but also used to inspect the welded parts.

Security check points in airports use x-ray to scan luggage without opening them. And police and army uses truck scanners with x-rays to scan the truck crossing the boarder.

Gamma Rays

Non contact industrial sensors use gamma rays to measure level, density and thickness.

Gamma rays are used in sterilizing medical equipment.

Just like the x-rays, Gamma rays are used in curing cancer too.

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