Laser and characteristics of laser

LASER means "LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION." It is a device which is used for producing highly intense, strongly monochromatic, highly coherent and collimated beam of light.

Characteristics of laser :

(1) Monochromatic Light: A light of single wavelength or frequency is called monochromatic light.
Laser light is highly monochromatic light i.e. all the photons have same energy above the ground energy state E1 and same frequency i.e.f=(E2 - E1)/h where E2 is the energy of excited state and h is Planck's constant.

(2) Coherent light:  A light in which all the photons or waves are in same phase with one another is called coherent light.
Laser light is highly coherent in nature.
* Incoherent light: The individual photons are not in phase with one another is called  incoherent light.

(3) Intense light: A coherent light in which all the photons are in phase is called an intense light. The amplitude of coherent wave is n × a and the resultant intensity is proportional to (na)×(na).

(4) Directionality: Laser light is highly directional. They spread very less as compared to ordinary light, hence are very useful for alignment purposes.

(5) Energy: Laser light is highly energetic. It can produce very high temperature when allowed to fall even at a spot. Therefore, laser is highly useful in cutting and welding.

(6) Focusing: Laser waves can be refracted and so can be focused on a spot of dimensions of the order of wavelength of light. This property is extremely useful in medical applications.