A How can a 10 Watt laser be much more dangerous than a 100W

A) How can a 10 Watt laser be much more dangerous than a 100W lightbulb?

B) When making a laser, why are at least 3 atomic energy levels needed?

C) What is the purpose of the mirrors on a laser cavity?

Solution

A) All of the lasers produce less light output than a 100 watt light bulb. But the bulb\'s light (and heat) spread throughout a room(say), while the laser\'s light is concentrated into a single beam. Even a ½ Watt laser pointer can make a dot that can be seen on a lit 100 watt light bulb. The laser is putting more visible light on the area of the dot, than the light bulb .The laser\'s wave length significantly affects how bright it appears. 10Watt may be a small amount of power but all that comes down a precise beam, in the same phase, at the same time. Your eye is a lens and focuses it into an even smaller spot, burning the retina.

B) the three levels are

C)Laser uses mirrors to reflect photons in order to stimulate atoms to emit photons. Lasers are pumped, so that many electrons already have excited states. In such a situation, when a photon passes through the active material, it\'s unlikely to be absorbed because there\'s not enough electrons in non-excited states. Much more likely result is that, by mechanism of stimulated emission, excited electrons can lose their energy, producing a duplicate of the photon which passed by. This happens when passing photon has energy very close to energy of radiative transition from excited state to non-excited. Mirrors make up the optical cavity, which makes photon travel multiple times across the active material, thus making more and more photons duplicate, resulting in exponential growth of electromagnetic energy, which partially exits the cavity because one (or both) of mirrors are not 100% reflective. And the light which exits is the usable light from laser.