Electromagnetic Spectrum

The electromagnetic spectrum encompasses the full range of electromagnetic radiation, which includes waves of varying frequencies and wavelengths. It spans from the longest wavelength (radio waves) to the shortest (gamma rays). Key types within the spectrum include microwaves, radio waves, infrared, visible light, ultraviolet rays, X-rays, and gamma rays. Each type has unique properties and applications, such as communication, medical imaging, and remote sensing. Understanding the electromagnetic spectrum is crucial in fields like physics, medicine, and technology.

1.0Definition of Electromagnetic Spectrum

The orderly distribution of electromagnetic waves in accordance with their wavelength or frequency into distinct groups having widely differing properties is called the electromagnetic spectrum.
The various regions of the electromagnetic spectrum do not have sharply defined boundaries and they overlap. The classification is based roughly on how the waves are produced or detected.

2.0Electromagnetic Waves in EM Spectrum

The electromagnetic spectrum spans from radio waves to cosmic rays, listed in increasing frequency and decreasing wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays, and cosmic rays.
The different types of radiation within the electromagnetic spectrum, along with their respective frequency and wavelength ranges, are as follows:

pictorial representation of electromagnetic spectrum and their wavelengths and frequencies.

3.0Waves Generation

Radio: A radio receives waves from stations, while gases and stars in space also emit radio waves. These waves are mainly used for TV and mobile communication.
Microwave: Microwave radiation aids in cooking and helps astronomers study galaxies and stars.
Infrared: Infrared light, used in night vision goggles, detects heat from our skin and objects. In space, it aids in mapping interstellar dust.
X-ray: X-rays are used in medicine for imaging, in airport security for scanning luggage, and are emitted by hot gases in the universe.
Gamma-ray: Radiations with the highest frequency and the shortest wavelength, making them the most penetrating waves.
Ultraviolet: Sun is the leading source of ultraviolet radiation, responsible for skin tanning and burns. Hot objects in space also emit UV radiation.
Visible: Our eyes can detect visible light, which is emitted by sources like light bulbs and stars.

Example-1. What physical quantity is same for X-rays of wavelength $1 0^{- 10} m$ red light of wavelength 6800 Å and radio waves of wavelength 500 m?

Solution: The wave speed in vacuum is the same for all radiations: $c = 3 \times 1 0^{8} m / s$

Example-2. A radio can tune to any station in the 7.5 MHz to 12 MHz band.What is the corresponding wavelength band?

Solution:

$v_{1} = 7.5 M Hz = 7.5 \times 1 0^{6} Hz$

$λ_{1} = \frac{c}{v _{1}} = \frac{3 \times 1 0 ^{8} m / s}{7.5 \times 1 0 ^{6}} = 40 m$

$v_{2} = 12 M Hz = 12 \times 1 0^{6} Hz$

$λ_{2} = \frac{c}{v _{2}} = \frac{3 \times 1 0 ^{8} m / s}{12 \times 1 0 ^{6}} = 25 m$

Thus the wavelength band is 40m-25m

4.0Wireless Communication Bands

Frequency band	Service
540-1600 kHz	Medium wave AM band
3-30 MHz	Shortwave AM band
88-108 MHz	FM broadcast
54-890 MHz	TV Waves
840-935 MHz	Cellular Mobile radio

5.0Electromagnetic Waves In Daily Life

Type	Wavelength Range	Production	Application
Gamma Rays	$[< 1 0^{- 3} nm]$	Radioactive decay of the nucleus	Gamma rays used in medicine to destroy cancer cells
X-rays	$[< 1 0^{- 3} nm t o 1 nm]$	X-ray tubes or inner shell electrons	Treatment of certain types of cancer
Ultraviolet Rays	$[1 nm t o 400 nm]$	Inner shell electrons in atoms moving from one energy level to a lower level energy level to a lower level	LASIK eye surgery, Water purifiers
Visible Rays	$[400 nm t o 700 nm]$	Electrons in atoms emit light when they move from one energy level to a lower energy level	Part of the electromagnetic spectrum detected by the human eye.
Infrared Rays	$[700 nm t o 1 mm]$	Vibration of atoms and molecules	Remote of TV, video recorders
Microwave	$[1 mm t o 0.1 m]$	Klystron valve or magnetron valve	Radar systems, microwave ovens
Radiowave	$[> 0.1 m]$	Rapid acceleration and deaccelerations of electrons in aerials	Radio communication like TV, radio, mobile communication etc.