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# Electromagnetic Spectrum

The propagation of light occurs like wave which is just like the flow water waves. The light waves are electromagnetic waves which are formed by electric and magnetic field. The electromagnetic spectrum consists the waves of all ranges of wavelength or frequency. It consists the harmful rays like IR rays and also some useful rays like radio wave for communication, X-rays for medical purpose, microwaves for cooking etc. this spectrum shows the range of energy of the rays.

The wave energy depends on the frequency of the waves and it increases with increasing the frequency while decreasing with wavelength. What do you think? Can we see all types of radiations that consist in electromagnetic spectrum? The answer is no, we can see only visible rays like visible spectrum rainbow. We can see all seven colours of rainbow easily. Here we are discussing the electromagnetic spectrum in detail with range of frequency or wavelength of all rays. Let’s discuss that.

## What is the Electromagnetic Spectrum?

The Electromagnetic radiations are a form of energy which are emitted and absorbed by the charged particles. These radiations exhibit the wave like behavior while it travels through the space. Electromagnetic waves have electric as well as magnetic field which are orthogonal to each other and also to the propagation of the waves.
These radiations composed of several types of waves in different wavelength and frequency regions. These frequencies and wavelength are described with the help of electromagnetic spectrum. The Electromagnetic spectrum categorizes waves with different frequencies and wavelength according to their wave characteristics, uses and applications.

## Electromagnetic Spectrum Frequency

The Electromagnetic spectrum is divided into several regions based on different frequencies, wavelengths and their characteristics. The figure shown below shows the Electromagnetic Spectrum Diagram which consists of all the em waves with respect to the wavelength and frequencies.

The Regions of the Electromagnetic Spectrum are as follows:

These waves are majorly used for communication. These radio waves are further divided into several bands extending from extremely low frequency to extremely high frequencies. Although different geography have different notions for different frequencies but the entire band is commonly used for communication worldwide.

Microwave:
These waves are initially thought of no use, but with research it is now-a-days used for several purposes. The initial use of the microwave is in long range communication but with time it is also used for heating the food.

Infrared wave:
The infrared wave lies between 300 GHz to 405 THz and hence the infrared wavelength is in between 750 nm - 1 mm. The near infrared lies between 0.75-1.4 $\mu$m wavelength range of infrared region while the far infrared lies between 15 - 1000 $\mu$m wavelength range of infrared region. Infrared spectrometers are generally used to study the Vibrational Spectra of molecules.

Visible light :
The frequencies in this region can be sensed by our eyes and interpreted as colors ranging from violet to red. With the violet having shorter wavelength and higher frequency while the red color have higher wavelength and shorter frequency.

Ultraviolet wave or rays :
The ultraviolet rays lie above the visible spectrum and are invisible to our eyes. These waves can be felt as sun burns.

X-rays :
The X-rays lie above the ultraviolet band and are produced by the sudden stoppage of the high speed charged particle by the use of metal target which absorbs these particles and hence the x-rays are emitted by such particles.

Gamma rays :
The Gamma rays are of extremely low wavelength and are produced by the radioactive decay of the radioactive atoms.

The Electromagnetic radiation spectrum consists of all the waves whether it is waves with the sub meter wavelength or wavelength in excess of kilometers.

The Electromagnetic radiation spectrum consists of the following electromagnetic waves:
1. Gamma ray
2. X-ray
3. Ultraviolet rays
4. Visible rays
5. Infrared rays
6. Microwave

## Electromagnetic Spectrum Chart

The EM spectrum is discussed in the form of a chart depicting the electromagnetic spectrum frequency, Electromagnetic Spectrum Energy, and electromagnetic spectrum wavelength of each region of the EM Spectrum.

 Name Wavelength Frequency (Hz) Photon Energy (eV) Gamma ray Less than 0.01 nm more than 10 EHz 100 kev - 300+ GeV X - ray 0.01 - 10 nm 30 EHz - 30 PHz 120 eV - 120 keV Ultraviolet 10 nm - 400 nm 30 PHz - 790 THz 3 eV - 124 eV Visible 390 nm - 750 nm 790 THz - 405 THz 1.7 eV - 3.3 eV Infrared 750 nm - 1 mm 405 THz - 300 GHz 1.24 meV -1.7 eV Microwave 1 mm - 1 meter 300 GHz - 300 MHz 1.24 $\mu$ eV - 1.24 meV Radio 1 mm - km 300 GHz - 3 Hz 12.4 feV - 1.24 meV

In the above table the Electromagnetic Spectrum Energy of all the frequencies is given. The Electromagnetic Spectrum Energy is measured by :
E = hf
Where,
h = Planck constant,
f = Frequency of the radiation and
E = Energy of the radiation.

## Microwaves Electromagnetic Spectrum

The Microwave region in the EM spectrum lies between 300 MHz to 300 GHz which roughly comprises of the UHF and EHF bands of the radio waves. In the older time the microwaves are defined as wave with the wavelength in the range of micrometers.
In the below chart we will discuss different bands in the microwave region of the EM spectrum given by the Royal Society of Great Britain.

 Letter Designation Frequency Range L band 1 to 2 GHz S band 2 to 4 GHz C band 4 to 8 GHz X band 8 to 12 GHz Ku band 12 to 18 GHz K band 18 to 26.5 GHz Ka band 26.5 to 40 GHz Q band 33 to 50 GHz U band 40 to 60 GHz V band 50 to 75 GHz E band 60 to 90 GHz W band 75 to 110 GHz F band 90 to 140 GHz D band 110 to 170 GHz

Although these bands are not exhaustive but are mostly used in the communications these days also. There are several other organizations which gives different bands as per the use. The organizations like ITU-T divide the microwave band according to its use in long distance communication. The microwaves like other EM waves are harmful for us. The extended exposure to microwaves can cause cancer in human tissues. It can also produces cataracts in our eyes.

The electromagnetic spectrum radio wave is shown in below figure.

As can be seen from the above diagram the radio wave band is further divided into the several bands depending upon their frequencies.

## Infrared and Ultraviolet Spectrum

The Infrared region consists of three bands:

Near infrared region:

The near infrared region is nearer to the visible region and they doesn’t have thermal characteristics.

Mid infrared region:
These infrared is used in telecommunication, communication, thermal imaging etc.

Far infrared region:
These are used in understanding the infrared emission from the deep space celestial objects and bodies.

Ultraviolet region:
The UV region consists of wavelength above the visible region and the natural source of these waves or rays is our Sun. The other sources of UV wave are celestial bodies far from our planet.
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