Register to reply

What is the wavelength of the light?

by atsum
Tags: light&#, wavelength
Share this thread:
atsum
#1
Oct27-12, 12:18 AM
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?
Phys.Org News Partner Chemistry news on Phys.org
Chemists modify antibiotic to vanquish resistant bacteria
Abnormal properties of cancer protein revealed in fly eyes
Rooting out horse-meat fraud in the wake of a recent food scandal
Simon Bridge
#2
Oct27-12, 01:08 AM
Homework
Sci Advisor
HW Helper
Thanks
Simon Bridge's Avatar
P: 13,093
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.)
atsum
#3
Oct28-12, 01:15 AM
P: 9
Quote Quote by Simon Bridge View Post
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.

Simon Bridge
#4
Oct28-12, 01:58 AM
Homework
Sci Advisor
HW Helper
Thanks
Simon Bridge's Avatar
P: 13,093
What is the wavelength of the light?

But I got a different order of magnitude from you.
Repeat the calculation ... you have misplaced a decimal point someplace.


Register to reply

Related Discussions
Betelgeuse will go supernova?? Astronomy & Astrophysics 10
Intensity of light / measuring wavelength of light Introductory Physics Homework 2
Does light emitted from the edge of the sun have a different wavelength than light em Astronomy & Astrophysics 11
Light-wavelength calculation General Physics 7
Wavelength of light General Physics 3