How do I solve this physics problem involving a laser?

laser eye surgery 0 image

Brandon

(a) In the stimulated emission for a certain laser, the photons arise from a transition between energy levels 2.24 eV apart. What is the wavelength of light emitted by this laser?

(b) Lasers are now used in eye surgery. Given that the wavelength of a certain laser is 514 nm and the power of the laser is 1.8 W, how many photons are released if the laser is used for 0.052 s during the surgery?

Answer
a) the energy between the levels is 2.24eV * 1.60x10^-19J/eV = 3.584x10^-19J

Now we have E = h*f so f = E/h = 3.584x10-19/6.63x10^-34 = 5.4057x10^14Hz

So λ = c/f = 3.00x10^8m/s/5.4057x10^14Hz = 5.550x10^-7m = 555.0nm

b) If λ = 514nm then f = c/λ = 3.00x10^8/514x10^-9 = 5.8366x10^14Hz

So E = P*t = n*h*f

So n = P*t/(h*f) = 1.8W*0.052s/(6.63x10^-34*5.8366x10^14) = 2.42x10^17 photons

How bad can your be to still be able to be in the Air Force?

Ari

So I want to be in the air force. But my eyes are at -4. I wear contacts that bring my eyes to 20/20. What is the cut off for how bad your eyes be before you cant be in the US Air Force/fly the planes? Can you do Laser Eye surgery to fix your eyes? Why do you have to wear glasses while in boot camp???

Thanks!
-Ari-

Answer
The max is + or - 8.0... Im not really sure how the vision scale works (I've never had vision problems) so idk if you fall within that. However, that is just to enlist, certain jobs (probably pilot) require better vision.

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