Question

What are the three characteristics of lasers?

Answer 1

In order to solve this question we need to understand absorption and emission of photon. So mainly at quantum level or microscopically energy is no longer continuous rather than it is discrete in nature. So at very low temperature electrons prefer to be ground state or low energy state, now is photon strikes this electron at low energy state then it absorbs this photon and get excited to a higher level energy states this phenomena is knows as absorption. Now at higher excites state electron resides for very short interval of time in microseconds, and it return back to its lower state by releasing photon this phenomena is known as emission.

Complete step by step answer:
Laser or Light Amplification by Stimulated Emission of Radiation is an electron device which produces a more focused and intense light beam. Actually the normal emission is spontaneous in nature but for a sustainable laser beam we need the electron to be at a higher excited level for more duration of time, and this could be done using metastable states having energy between lower and higher excited states and an electron in his state can stay for a longer duration of time.

Three characteristics of laser are;
(i) Laser beams are monochromatic in nature: Monochromatic means the laser beam has only one wavelength of visible light in it. Monochromatic beam is produced because a de-exciting electron releases a photon of single wavelength.

(ii) Laser beams are unidirectional: Unidirectional means laser beams can only propagate in one direction unlike the other light sources like light bulb etc. which sends the wave of light in all possible directions.

(iii) Laser beams are of high intensity: High Intensity laser beams are due to fact that the photons emitted would locked in a chamber where they suffer multiple collisions and finally they are being released from a tiny hole and hence the laser beams are of high intensity.

Note: It should be remembered that during production of laser beams stimulated emission occurs while in ordinary emission spontaneous emission occurs. We need electron to be at more duration at higher energy excited level so that a photon might strike this electron at higher states and hence when it de-excites it releases two photons in place of one and the released photons could initiate a chain of emission of photons, this is known as stimulated emission and this is how laser beams are produced.