Electromagnetic Waves in Electromagnetic Spectrum

Electromagnetic radiation (EMR) is a kind of radiation in which electromagnetic (EM) field waves carry radiant energy through space. Electromagnetic radiation includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic spectrum consists of all these frequencies. Electromagnetic waves are produced when electric particles are accelerated, interacting with and exerting force on other charged particles. Energy, momentum and angular momentum can all be transferred from a source particle to the substance it interacts with. 

Maxwell was the first scientist to predict the presence of electromagnetic waves. These waves were produced and detected by Hertz. Another scientist called JC Bose produced an electromagnetic range of wavelength between from 5 to 25 milimeter. Successful transmission of electromagnetic waves up to a few kilometres was done by Macaroni. 

Electromagnetic Spectrum

Electromagnetic spectrum or EM spectrum is just a distribution of electromagnetic radiations in a given order based on their wavelength and frequency.

This spectrum is the foundation of the information age and of our modern world. Your radio, remote control, text messages, television, oven, even doctor’s x-ray, all depend on waves with electromagnetic spectrum.

Now, let’s talk about electromagnetic waves.

Electromagnetic Waves

• Electromagnetic waves are produced by the vibration of charged particles and have electric and magnetic properties.

• EM waves travel through the vacuum of space at the constant speed of light.

• They have crests and troughs.

• The distance between any two crests or two troughs. This is known as the wavelength of the given EM wave.

• Number of crests that pass a given point within 1 second is described as the frequency of the wave. One wave or cycle per second is called hertz.

Some EM waves are very long and are measured in metres (m), many are tiny and are measured in nanometers (nm). Long EM waves, such as radio waves have the longest frequency and carry less energy. Adding energy increases the frequency of the waves and makes the wavelength shorter.

• Gamma rays are the shortest, highest energy waves in the spectrum.

Electromagnetic Spectrum in our surroundings 

So, as you sit watching TV, not only are these visible light waves from the TV striking to your eyes, but also, radio waves are coming from a nearby station and microwaves carrying phone calls and also the waves from your Wi-Fi are electromagnetic in nature.

There are a number of waves from all across the spectrum passing through your room right now! Can you imagine?

Fact-1

With all these waves around you, how can you possibly watch a TV show? 

It is similar to turning a radio to your favourite radio station, our eye detects energy with wavelength ranges between 400 nm to 700 nm, the visible light region of the spectrum.

Fact-2

Why do objects appear to have colours?

As Electromagnetic waves interact with their molecules, some wavelengths in the visible spectrum are reflected and other wavelengths are absorbed. For example, a leaf looks green because electromagnetic waves interact with the chlorophyll present in the molecules of the leaves of the plant and reflect only green.

Electromagnetic Waves in Electromagnetic Spectrum

The electromagnetic spectrum is classified into the following main parts, that are mentioned below in the order of increasing frequency.

1) Radio Waves: Wavelength range is > 0.1 m

Radio waves are the longest waves and contain the least energy of the EM waves. These waves vary from about the length of a water bottle, to waves the length of cars, ships, mountains, all the way up to waves longer than the diameter of the earth. Heinrich Hertz discovered these waves in 1888. Many of the greatest astronomical discoveries have been made using radio waves. We can’t hear these. When we tune our radio to our favourite station, the radio receives these EM radiations and vibrates a speaker to create the sound waves.

Uses: 

• Used in ground wave propagation.

• Used in sky wave propagation.

• Used in television waves.

• Used in FM radio.

• Used in cellular phone communication.

2) Microwaves: Wavelength range varies from 0.1 m to 1 mm

These waves can pop your popcorn. These waves can catch you speeding. These carry 1000s of phone channels to speed our calls. These waves fall between infrared and radio waves. They are the backbone of communications and Earth sensing systems.

Uses:

• Used in radar systems of aircraft systems.

• These can detect the speed of a vehicle and even the speed of a cricket ball.

• Microwave ovens use them.

3) Infrared Waves: Wavelength varies from 1 mm to 700 nm

When we use remote controls to change channels on our television, our remote is using light waves. But, this light wave is beyond the visible spectrum of light that we can see. We can sense some of this infrared as heat. They have longer wavelengths than visible.

Uses:

• Used in physical therapy.

• Used to provide electrical energy to satellites.

• Used in producing dehydrated fruits.

• Used in solar water heaters and solar cookers.

• Used to see astronomical phenomenons.

4) Visible Rays: Wavelength varies from 700 nm to 400 nm

All EM radiation is light. It is the only part of the spectrum that we can see.

Uses:

• To see our beautiful world.

• In photography, to take pictures.

5) UV Rays: Wavelength varies from 400 nm to 1 nm

Light beyond violet, UV rays. Visible rays from the sun pass through the atmosphere and reach earth’s surface. These may be harmful to humans, but they are essential in studying the health of our planet’s protective atmosphere and give us valuable information.

Uses:

• Used to destroy bacteria.

• Used to preserve foodstuff.

• Used in lasik surgery.

• Used to kill germs in a water purifier.

6) X-rays: Wavelength varies from 1 nm to 0.0001 nm

These are very high energy light waves. So small that some of them are not even bigger than many individual atoms. Also, these rays play a vital role in calculating the object’s temperature.

Uses:

• Used in surgery to detect fractures.

• Also used in detecting metal cracks and faults in engineering.

• Used in X-ray diffraction to find the structure of a given crystal.

• Used to detect some astronomical objects.

7) Gamma Rays: (Wavelength ranges < 0.0001 nm)

These rays are created on Earth by natural radioactive decay, by nuclear explosions, even by the lightning during thunderstorms.

The most energetic of all the EM waves, these waves carry enough energy to kill living cells. Doctors are able to selectively use these radiations to destroy cancer growths. Wavelengths are also shorter than all EM waves and are about the size of the atom’s nucleus.

Uses:

• They play a vital role in the treatment of cancer.

• Used to produce nuclear reactions.

• Also provide valuable info about the structure of the atomic nucleus.

Conclusion

We have gone through all the portions of the electromagnetic waves in the electromagnetic spectrum. We have learned the importance of the EM spectrum in our day life and also seen how these radiations are being very helpful in detecting upcoming weathers, new discoveries in the galaxy, and also made it easy for scientists to detect the upcoming radiations. 

The basic difference between various types of electromagnetic waves lies in their wavelengths of frequencies since all of them travel through vacuum with the same speed. Consequently the Waves differ considerably in their mode of interaction with the matter. 

Infrared waves with frequencies lower than that of visible light vibrate not only the electrons but the entire molecule or atom of a substance, this vibration increases the internal energy and hence the temperature of that particular substance this is why, why these waves are called heat waves. The centre of sensitivity to our eyes coincides with the centre of the wavelength distribution of the sun, it is because humans have evolved with visions most sensitive to the strongest wavelength from the Sun. 

These electromagnetic waves are responsible for many scientific developments which we see today and have been a major part of our lives, as they have many practical implications.