# LASER Problems HELP NEEDED!

1. May 19, 2010

### SAT2400

LASER Problems!! HELP NEEDED!

1. The problem statement, all variables and given/known data

1. The carbon dioxide laser usually emits at 10.6 um in the IR. Typically such a device puts out a continuous emission of from a few watts to several kilowatts. Determine the energy difference in eV between the two laser levels for this wavelength.

2. A certain variation of He-Ne laser operates btwn two levels that are 3.655 x10^-19J apart. What color is the beam? comupte the wavelength.

2. Relevant equations
delta(E)=hc/^
^=wavelength

3. The attempt at a solution
1. answer is .117eV ..(6.63x10^-34)(3x10^8)/(10.6x10^-6)??but didn't get it
2. answer is 543.5 nm( green)...3.655 x10^-19J =hc/^

2. May 19, 2010

### mgb_phys

Re: LASER Problems!! HELP NEEDED!

Correct - the energy of a photon is E = h * frequency = h c / wavelenght

As long as you get the numbers correct in your calculator thats all there is to it - be careful that if 'c' is in metres your wavelength will also be in metres

3. May 19, 2010

### SAT2400

Re: LASER Problems!! HELP NEEDED!

c=3x10^8 right?
can you explain more...??tHanks

4. May 19, 2010

### mgb_phys

Re: LASER Problems!! HELP NEEDED!

Explain why E = h * frequency ?
It's rather complex ( see http://en.wikipedia.org/wiki/Planck_constant)

c = 3x10^8 m/s (remember units matter!)
h = 6.6x10^-34 Js

So energy (J) = h (Js) * frequency (1/s), check that the units cancel

And since speed, c = frequency * wavelength you can rearrange this to give you
Energy (J) = h (Js) c (m/s) / wavelength (m), again the units cancel out to give you J

5. May 19, 2010

### SAT2400

Re: LASER Problems!! HELP NEEDED!

I already knew the equation...but I was not sure if I used the right numbers,,,??
h=6.63x10^-34Js c= 3x10^8m/s

whatelse??

thanks

6. May 19, 2010

### mgb_phys

Re: LASER Problems!! HELP NEEDED!

For the first part of the problem it asks for the energy in eV
h = 4.14 x 10^-15 eV s

7. May 19, 2010

### SAT2400

Re: LASER Problems!! HELP NEEDED!

ahhh got it! THank you! :)

Can you please answer my other questions??(uncertainty problems?)