vpoko your a star.

I know im not a physics buff but i do know how a laser works and mabye I worded it wrong but pumping materials with photons at a given wavelength does produce that material to emit photons.

Derstrom8 try googling something called stimulated emission.

Thanks again for all the replies!!

 

Derstrom8 try googling something called stimulated emission.

I know what stimulated emission is, but I misunderstood your original post. I apologize for my error.

 

To be honest i do not even know what my original post is haha!! I must say that this is an excellent forum everyone is very helpful!!

 

Google "entropy". It is a subject many people have problems with.

Light is energy. It gets used up unless replenished.

Funny thing, I did not realize there were 3 pages of replies when I posted this.

 

"Olbers paradox"

(You might get some education)

What I got is

 

Have you checked out this link.......
https://www.msu.edu/user/dynicrai/physics/dark.htm

 

http://en.wikipedia.org/wiki/Stimulated_emission

Read the overview section

In that overview,if you read it properly,it tells you that the only time you can get Stimulated emission is if there is a population inversion.

The only way you can get such a condition is to supply energy from some external source,(RF energy for a MASER,light energy for a conventional LASER,& DC energy for a semiconductor LASER.

Once the external energy is removed,Stimulated emission ceases,just as light emission from an incandescent light bulb ceases when the external energy source is removed.

 

Never mind the light bulb. The big question is: Why is it dark at night?

Obvious? Think again. Google "Olbers paradox"

(You might get some education)

Damn, I caught this thread late and read the whole thing so I could post that same question.

Off the top of my head I would expect the night sky to be about as bright as the surface of the sun as seen in the day.

 

In that overview,if you read it properly,it tells you that the only time you can get Stimulated emission is if there is a population inversion.

The only way you can get such a condition is to supply energy from some external source,(RF energy for a MASER,light energy for a conventional LASER,& DC energy for a semiconductor LASER.

Once the external energy is removed,Stimulated emission ceases,just as light emission from an incandescent light bulb ceases when the external energy source is removed.

It would appear that some people do not read the initial post. I never said once that random photons will produce stimulated emission. I was using that link to show that materials do absorb photons and reproduce photons through the process of stimulated emission. Also the way a laser works is through population inversion, now you can still get stimulated emission without population inversion its just that you cannot keep it going and it will eventually cease. Population inversion is what a optical amplifier needs to function over a continued period of time. Stimulated emission can in theory still happen without it, granted that it would not last

 

It would appear that some people do not read the initial post. I never said once that random photons will produce stimulated emission. I was using that link to show that materials do absorb photons and reproduce photons through the process of stimulated emission. Also the way a laser works is through population inversion, now you can still get stimulated emission without population inversion its just that you cannot keep it going and it will eventually cease. Population inversion is what a optical amplifier needs to function over a continued period of time. Stimulated emission can in theory still happen without it, granted that it would not last

I am only going by the text of your original linked page.

"In normal media at thermal equilibrium, absorption exceeds stimulated emission because there are more electrons in the lower energy states than in the higher energy states. However when a population inversion is present the rate of stimulated emission exceeds that of absorption, and a net optical amplification can be achieved. Such a gain medium, along with an optical resonator, is at the heart of a laser or maser."

If Stimulated emission does occur,& not last,perhaps the room does stay lit for such a small time after you switch it off,that our human senses do not perceive it.

It would have to be a very short time,as otherwise it would be a source of error in the duration of Electronic Photographic flash equipment.
Human eyes would not see a delay of around 25mS,but that would be large enough to be discernible with fast flash gear.