GR9677 #40



Alternate Solutions 
BerkeleyEric 20100922 22:36:21  I think process of elimination is fastest here. From the Bohr formula we know that the n=1 is at 4*(13.6 eV) ~ 52 eV. So it can't be (D). And it also can't be (B) since the n=2 state wouldn't be all the way up at 6 eV.
Now remember that 470 nm falls in the visible regime, so the energy difference must be at around 12 eV. This immediately eliminates (C) and (E) since they must be more than this amount lower than the n=4 state.   archard 20100715 13:50:25  You can also get it with the Rydberg formula, since you're given the wavelength of the photon and the initial energy level. Then it's just plug and chug.  

Comments 
cczako 20131018 15:21:38  The way I did was to just remember that E is proportional to Z^2/n^2. Its quick and easy to calculate that n=4 > E= 3 eV, n=3 > E=6 eV, n=2 > E=13.6 eV, and n=1 > E=50 eV. This automatically eliminates B and D. Then using the equation E=(hc)/lambda (I always use 1240 nm*eV for hc) you get that 470 nm is about 3 eV. So n=4 of energy 3 eV minus 3 eV gives you 6 eV. This gives you choice A.   BerkeleyEric 20100922 22:36:21  I think process of elimination is fastest here. From the Bohr formula we know that the n=1 is at 4*(13.6 eV) ~ 52 eV. So it can't be (D). And it also can't be (B) since the n=2 state wouldn't be all the way up at 6 eV.
Now remember that 470 nm falls in the visible regime, so the energy difference must be at around 12 eV. This immediately eliminates (C) and (E) since they must be more than this amount lower than the n=4 state.   archard 20100715 13:50:25  You can also get it with the Rydberg formula, since you're given the wavelength of the photon and the initial energy level. Then it's just plug and chug.
sina2 20130924 02:17:02 
I tried in this way, but I failed.

nasim 20151012 17:05:01 
One should first have the Rydberg constant to be able to use Rydberg formula! But doesn\'t!

  asdfman 20091105 00:37:16  You can quickly narrow this down as anything less than ~400 nm is UV. If you remember that 13.6 eV, from hydrogen yields UV then that tosses out choices C, D, and E.   f4hy 20091025 19:28:33  I am confused. When finding are you using the speed of light in cm but the wave length in meters?
kroner 20091029 14:13:19 
Everything is in meters there.
eV m or 1240 eV nm,
which good value to know offhand for problems like this.

  astro_allison 20051208 22:50:07  don't you mean ?  




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