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Expert: Daniel Mazur - 8/1/2005


Question
How much energy in eV (electron-volts)is emitted by a hydrogen atom if the electron jumps from the n=5 level to the n=2 level? What is the frequency of the light emitted? What is the wavelength of the light emitted?

15 - High School - Australia

Answer
You can find answer to this question at

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

clicking at "Quantum Physics" and then "Hydrogen Spectrum" in the navigation charts.

I will, though, write down the answers here.
deltaE ... energy emitted
freq ... frequence of light
lambda ... wavelength of light

deltaE = (-13.6eV)*(1/n_1^2 - 1/n_2^2), n_1=5, n_2=2 ->
  -> deltaE = 2.856 eV = 4.576e-19 J
freq = deltaE/h_planck, h_Planck = 6.626e-34 J.s ->
  -> freq = 6.906e+14 Hz
lambda = c*h_Planck/deltaE, c = 2.998e+8 m/s ->
  -> lambda = 4.341e-7 m

Here you are, contact me again, if you have further questions.
Daniel

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Questions anyone (teenager, undergrad, graduate, professional) may ask on physics, mathematics or inorganic chemistry. Questions may concern subjects themselves or a possible future career in them, if you need advice on a school or hobby project, or you just came across a question that is beyond your current curriculum. I answer bare textbook problems sometimes, but I reserve the the right to redirect you to Physics-Physics section. The kind of questions I like to answer: I just started having science classes at school and they seem difficult, but I enjoy them. Where do I find more information on this, which is not in textbooks but still comprehensible to me? Just leaving high school, and I feel science is really the thing for me. Can you recommend a school and an undergrad program suitable to my inclinations? I am in my second undergraduate year in Physics. We learned the basics of universe expanding this year, the Hubble constant and all that, but invited speakers that gave talks on astrophysics in our department seemed not to agree with this model at all. Is it of any use at all? I am building a [materials research] experimental device for my masters/doctorate thesis and I have the following problem:... I have tried ..., but it still doesn't work. Where might the problem be?

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