1.57 [ENDORSED]

[Alex Kashou]

Lines in the Balmer series of the hydrogen spectrum are observed at 656.3, 486.1, 434.0, and 410.2nm. What is the wavelength of the next line in the series.

Okay so I understand i need to use v=R(1/(n^2)- 1/(n^2)) (sorry its not perfect but you know the formula). I know the Balmer series starts n1=2 but the next n level that I need to find should be the n5=6 but in the answer sheet its 7.

Can someone explain to me why?

[sandros]

For the Balmer series, we know that n1=2. We also know that the difference between two energy levels is emitted as a radiation of a particular wavelength. This is called a spectral line. Therefore, the difference between E3 and E2 gives us the first spectral line of the Balmer series.
As we go on,
E4-E2= 2nd spectral line
E5-E2= 3rd spectral line
E6-E2= 4th spectral line
Finally, E7-E2= 5th spectral line (so the answer sheet is correct)

Once you get the concept, you should be able to find the wavelength using the Rydberg equation quite easily.
Hope this helps.