Microwaves:

It is produced by electromagnetic oscillators in electric circuits. The wavelength range is 1 x 10^-3 m to 3 x 10^-1 m and frequency range is 3 x 10¹¹ Hz to 1 x 10⁹ Hz. It obeys reflection and polarization. It is used in radar system for aircraft navigation, speed of the vehicle, microwave oven for cooking and very long distance wireless communication through satellites.

X-rays: 

It is produced when there is a sudden deceleration of high speed electrons at high-atomic number target, and also by electronic transitions among the innermost orbits of atoms. The wavelength range 10^-13 m to 10^-8 m and frequency range are 3 x 10²¹ Hz to 1 x 10¹⁶ Hz. X-rays have more penetrating power than ultraviolet radiation.

X-rays are used extensively in studying structures of inner atomic electron shells and crystal structures. It is used in detecting fractures, diseased organs, formation of bones and stones, observing the progress of healing bones. Further, in a finished metal product, it is used to detect faults, cracks, flaws and holes.

Radio waves: 

It is produced by oscillators in electric circuits. The wavelength range is 1 x 10^-1 m to 1 x 10⁴ m and frequency range is 3 x 10⁹ Hz to 3 x 10⁴ Hz. It obeys reflection and diffraction. It is used in radio and television communication systems and also in cellular phones to transmit voice communication in the ultra high frequency band.

Visible light:

It is produced by incandescent bodies and also it is radiated by excited atoms in gases. The wavelength range is 4 x 10^-7 m to 7 x 10^-7 m and frequency range are 7 x 10¹⁴ Hz to 4 x 10¹⁴ Hz. It obeys the laws of reflection, refraction, interference, diffraction, polarization, photo-electric effect and photographic action. It can be used to study the structure of molecules, arrangement of electrons in external shells of atoms and sensation of our eyes.