# Calculating the width of the box for a particle in a box (1 Viewer)

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#### tarletontexan

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

A ruby laser emits light of wavelength 694.3 nm. If this light is due to the transition from n=2 to n=1 state of the electron in a box, what is the width of the box?

2. Relevant equations

K=2pi/Lambda
kL=npi

3. The attempt at a solution
Thinkin about the problem, i have calculated K as shown in my formula to be 9049669 but when i use this k to find L then i end up with 694.3 again. I dont know if this is the answer or if this is a really big mistake???

#### fzero

Homework Helper
Gold Member
The K and k in those equations are not the same. $$K = 2\pi/\lambda$$ is the wavenumber of the emitted photon. $$k = n\pi/L$$ are the wavenumbers of the electron wavefunctions. You need to compute the difference in electron energy levels and equate that to the energy of the photon.

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