Electromagnetic Spectrum

What is Electro magnetic spectrum?
Electromagnetic spectrum is defined as all possible range of frequencies or wavelengths of electromagnetic radiation spreading from gamma rays to radio waves including visible light. In the early days, scientists assumed that the light consists of tiny particles called photons which travels at the speed of light i.e. 3*10^8 m/s. But this assumption did not satisfy certain conditions. Hence they arrived at a conclusion that light travels through space in the form of waves known as electromagnetic waves.

Electromagnetic waves:
Electromagnetic spectrum comprises of electromagnetic waves. Electromagnetic waves constitute similar kind of disturbances repeating at certain wavelengths. The definition of James Clerk Maxwell and Hertz is as follows,

"Electro magnetic waves are waves which comprises of electric and magnetic fields which are at right angles to each other, travels along the direction of the wave and are in phase with one another"

The different types of waves that constitute the electromagnetic spectrum are

Radio waves:
Radio waves have a frequency ranging from 10^3 – 10^6 Hertz and a wavelength of 10^4 to 10^ 1 m. These waves are used for radio and television broadcasts, mobile phones, government and non government services like aeronautical beacons. The FM stations require 200 KHz of frequencies for a maximum of hundred stations. The 25 KHz frequency range is known as guard bands which are used to minimize interference. Televisions require 5 MHz separation.

Micro Waves:
Micro waves are used in telephone satellites which are used to transmit the human voice in microwave code. Its frequency ranges from 10^6 – 10^10 Hertz and wavelength ranges from 10^1 to 10^ (-2) m. It has a very short wavelength that, it is easily absorbed by water. The microwave radiation generates molecular rotation and torsion which produces heat. For this purpose, it is used in microwave ovens. It is also used in electron spectroscopy.

Infrared waves:
Infrared waves forms the lower end of the visible spectrum with a frequency ranging from 10^10 – 10^14 Hertz and a wavelength of 10^ (-3) to 10^ (-6) m. They generate heat formed by the vibration of molecules and are used in infrared detectors, television remote controls etc.

Visible Light:
The narrow band of electromagnetic spectrum which is detected by the human eyes has the frequency of 10^14 Hertz and wavelength of 10^ (-6) m. They are produced by the ionization of electrons and retina of the eyes can sense only this range of wavelength. When white light is passed through a prism it splits to form seven different colors known as dispersion.

Ultraviolet Rays:
Ultraviolet rays have a very high energy whose frequency ranging from 10^14 – 10^16 Hertz and wavelength of 10^ (-6) to 10^ (-8) m. These rays are highly carcinogenic due to ionizing radiations but have some therapeutic features also. Sun is the source of UV rays and hone bees can detect it. This causes sun burns and affects the eyes during long exposure.

X-rays:
X-rays are highly penetrating rays formed when fast moving high energy electrons are stopped by a metal. Frequency range is from 10^16 – 10^19 Hertz and wavelength of 10^ (-8) to 10^ (-10) m. They are used to determine molecular structures and used in the medical field as they penetrate through flesh but long exposures are carcinogenic.

Gamma rays:
Gamma waves have a frequency greater than 10^19 Hertz and a wavelength less than 10^ (-10) m. They are produced by high energy processes and causes devastation when it strikes atoms or molecules. The gamma radiation produces physiological effects such as mutation, cancer etc.