# What is the wavelength of the light？

by atsum
Tags: light&#, wavelength
 P: 9 Calculate the wavelength of the light emitted when an electron in a one-dimensional box of length 5.2nm makes a transition from the n = 7 state to the n = 6 state. Express your answer with the appropriate units. I calculated in this way: E = n^2*h^2/8*m*a^2 E= (7^2-6^2)*(6.626*10^-34)^2/8*(9.1*10^-31)*(5.2*10^-9)^2 E= 2.9*10^-20 J E = hc/λ λ = 6.85*10^-6 m But the answer is wrong. What is wrong with my calculation?
 HW Helper Sci Advisor Thanks P: 9,029 How do you know the answer is wrong? It can help if you do the algebra first, then use more convenient units:$$\lambda=\frac{8(m_e c^2) L^2}{hc}\frac{1}{n_f^2-n_i^2}$$ ##hc=1.240\text{eV$\mu$m}## ##m_ec^2=511\text{eV}## ##L=0.0052\text{$\mu$m}## ... give it a go. (Don't forget to check my algebra to get that equation.)
P: 9
 Quote by Simon Bridge How do you know the answer is wrong? It can help if you do the algebra first, then use more convenient units:$$\lambda=\frac{8(m_e c^2) L^2}{hc}\frac{1}{n_f^2-n_i^2}$$ ##hc=1.240\text{eV$\mu$m}## ##m_ec^2=511\text{eV}## ##L=0.0052\text{$\mu$m}## ... give it a go. (Don't forget to check my algebra to get that equation.)
It is the same calculation as mine.
I did the exercise on MasteringChemistry. It only said my answer is wrong.

HW Helper