Electromagnetic spectrum

The arrangement of electromagnetic radiations, either in ascending or descending order of the wavelength and frequency, is called the electromagnetic spectrum. Electromagnetic spectrum various classes of electromagnetic radiations are identified, but there exists no sharp, clear-cut division between any two radiations, as the classification exists in ranges.

The electromagnetic wave was experimentally discovered by Hertz. The primary difference between various types of electromagnetic waves lies in their wavelength and frequencies, as all these waves travel at the same speed in the vacuum of free space. Though their mode of interaction with the particles of the medium extensively differs.

Types of the electromagnetic spectrum

The seven classes of electromagnetic waves include

• Radio waves
• Microwaves
• Infrared waves
• Visible light
• Ultraviolet rays
• X-rays
• Gamma rays

Radio waves

Radio waves are the types of electromagnetic waves that are produced by the accelerated motion of charges in conducting wires or oscillating electric circuits. They are extensively used in radio and television communication systems.

Properties of radio waves

• The frequency range lies between 500kHz and 1000MHz
• The wavelength range lies between 10-2 m and 104 m.
• The radio waves can be, reflected, refracted, and diffracted

 Uses of radio waves

• Amplitude modulated(AM) with the band of frequency 530 to 1710 kHz- used in ground wave propagation.
• Short waves(SW with the band of frequency 1710 kHz to 54MHz – used in sky wave communication.
• Television waves with the band of frequency ranging from 54 to 890MHz
• Frequency modulated(FM) with the band of frequency ranging from 88 to 108 MHz- used for FM communication
• Ultra-high frequency waves (UHF) with the band of frequency 300 to 3000 MHz- used in cellular phone communication. 

Microwaves

The microwaves are short-wavelength radio waves. These waves are produced by special vacuum tubes, called Gunn diodes, magnetrons, and klystrons.

The frequency range of microwaves

The frequency range of microwaves lies between 1 GHz and 300GHz

 Uses of microwaves

• Used in radar system for aircraft navigation, due to their short wavelengths
• Used to detect speeds of a tennis ball, Cricket ball, automobiles, etc.
• Used in microwave ovens

Infrared waves

Infrared waves are produced by hot bodies, that is, the vibrations of atoms and molecules. Such waves have low frequency and their wavelengths. They are present adjacent to the visible spectrum.

Properties of infrared waves

• The frequency range lies between 1011 Hz and 1014 Hz
• The wavelength range lies between 1m  and 700 nm.
• They have such characteristics that they are also known as heatwaves.
• They cannot be detected by human eyes, but snakes and certain insects can detect these waves. Not only this, some insects tend to detect higher ranges of the electromagnetic spectrum, like ultraviolet rays.
• These waves are readily absorbed by particles like carbon dioxide, ammonia, water molecules, etc. After getting absorbed by the above-mentioned particles, they heat their surrounding environment.
• Infrared waves are also responsible for maintaining Earth’s average temperature through the greenhouse effect.

Uses of infrared waves

• An infrared lamp is used in physical therapy to treat muscular strain.
• It is used as detectors, in earth satellites, in order to observe the growth of crops and for security purposes
• It provides electrical energy to satellites by using solar cells.
• It is used to take photographs during fog and smoke.
• It is used to study molecular structure by means of an infrared absorption spectrum.

Visible rays

Visible rays are a range of electromagnetic spectrum produced by atomic excitation. They are the only range that is sensitive to human eyes, as the visible light emitted or reflected from the objects makes us see the world around us. It is detected by the eyes, photocells, and photographic films. The frequency range lies between 4×1014 Hz and 7×1014 Hz. The wavelength range lies between 700 and 400 nm.

Ultraviolet rays

Ultraviolet rays are produced by the sun, special lamps, and very hot bodies. The frequency range lies between 8×1014 Hz and 5×1016 Hz. The wavelength range lies between 400nm  and 0.6 nm.

Uses of Ultraviolet rays

• Used in LASIK (Laser-assisted in situ keratomileusis), Eye surgery, that requires high Precision focussed narrow beam of ultraviolet rays.
• Used in UV lamps that are used to kill germs in water purifiers
• Used for the destruction of bacteria in hospitals and laboratory
• Used in sterilization of surgical instruments
• Used in exposure to ultraviolet radiation is harmful to both humans and aquatic animals.
• It restricts the entry of ultraviolet rays into the Earth’s atmosphere.

X-rays

X-rays are produced in a tube called a modern x-ray tube, also so when a metal target is bombarded with high-energy electrons, such waves are produced. The frequency range lies between 1016 Hz and 1021 Hz. The wavelength range lies between 10nm and 10-4 nm. These waves are detected by photographic films, Geiger tubes, and ionization chambers.

Exposure to X-rays can lead to the destruction of living tissues and can also be responsible for mutation (alteration of the genetic code) in extreme cases. Hence, it is advised for pregnant women to stay away from x-ray rooms.

Uses of X rays

• To detect cracks, fractures, and displacement in bones, as a Diagnostic tool
• Used in treatment for certain forms of cancer, under the name of radiotherapy
• Used in engineering to detect faults, for crack, flaws, and holes
• Used to detect pearls in oysters, defect in rubber tires, and gold

Gamma rays

There is the high-frequency race which is produced in nuclear reactions and is emitted by radioactive nuclei.

Properties of gamma rays

• The Frequency range lies between 1018 Hz and 1022 Hz.
• The Wavelength range lies between 10-10 m and 10-14 m.
• Waves show the properties like phosphorescence, fluorescence, polarization, and diffraction
• They have a very high penetrating power

Uses of gamma rays

• Used for cancer therapy, by destructing cancer cells
• Provide important information regarding the nuclear structure

Conclusion 

Spectroscopy is the study of how the different electromagnetic waves interact with the particles of the medium. We have discussed that electromagnetic waves interact with the particles, atoms, and molecules of the medium and hence alter the characteristics of electromagnetic waves.