# Quantum Mechanics (need help)

1. Dec 2, 2008

### s3b4k

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

1. A photon is emmited when an electron confinded to a box of length 10^-9 m undergoes energy level transition, and has a frequency of 2.50 x 10^15 Hz. Find the energy levels associated with emited radiation

2. Relevant equations

E=n^2h^2/8mL^2
E=Hc/wavelength
E= -13.61/n^2

3. The attempt at a solution

i have no clue

1. The problem statement, all variables and given/known data
compute the wavelength of an electron having speed a) 3 x 10^4 m/s b)0.1 x speed of light

2. Relevant equations

E=n^2h^2/8mL^2
E=Hc/wavelength
E= -13.61/n^2

3. The attempt at a solution

not sure

1. The problem statement, all variables and given/known data
A hydrogen discharge tube(lamp) is excited with energy 13.15 eV. How many possible lines would be obsererved in the emission spectrum of these atoms as a result of this exciation, and which ones would be visible. Visible range 4000A and 8000A

2. Relevant equations

E=n^2h^2/8mL^2
E=Hc/wavelength
E= -13.61/n^2

3. The attempt at a solution
something with factorial not sure how to though

Last edited: Dec 2, 2008
2. Dec 3, 2008

### buffordboy23

Initially, the electron is in some unknown stationary state. Then the electron emits a photon of "specific" energy and is now in a lower state. What is special about the energies associated with the different stationary states? They are quantized:

$$E_{n} = \frac{n^{2}\pi^{2}\hbar^{2}}{2mL^{2}}$$

Do you got it now? By the way, where did the 8 come from in your formula?

3. Dec 3, 2008

### s3b4k

im not sure its in my forumla book, where did you get the pie from i dont have that in the equation

4. Dec 3, 2008

### malawi_glenn

He is using h-bar.

$$\hbar = h/(2\pi )$$

And you have all the equations you need for this, why don't you make a serious attempt to solve it?
If you have NO clue, make a (motivated) guess!

5. Dec 3, 2008

### malawi_glenn

He is using equation with h, placks constat, you are using formula with h-bar. Be careful! :-)