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Help ! - computing a Balmer line
I've posted a simple OG spectrum of Comet Machholz and Algol at
http://home.freeuk.com/m.gavin/digsky.htm where the star records on the Canon CMOS sensor to the Balmer line H-lambda [line 11 where H-alpha = line 1 at 656.3nm] in near UV. Can someone compute the wavelength of H-lambda please? I've got the formula but don't think H-alpha = 1 and in any case my calculator's dead! |
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Maurice Gavin wrote:
I've posted a simple OG spectrum of Comet Machholz and Algol at http://home.freeuk.com/m.gavin/digsky.htm where the star records on the Canon CMOS sensor to the Balmer line H-lambda [line 11 where H-alpha = line 1 at 656.3nm] in near UV. Can someone compute the wavelength of H-lambda please? I've got the formula but don't think H-alpha = 1 and in any case my calculator's dead! I have the following list, the higher members of which I believe to have been computed on a day when my brain was fully engaged: Balmer 6562.80 H-alpha 4861.32 H-beta 4340.46 H-gamma 4101.73 H-delta 3970.07 H-epsilon 3889.05 H8 3835.38 H9 3797.90 H10 3770.63 H11 3750.15 H12 3734.37 H13 3721.94 H14 3711.97 H15 3646.0 Balmer limit (the numbering there is in the system in which it denotes the number n of the upper level for the transition, so your 11 is my 13...) In Angstroms, the formula would be wavelength = 911.75 / (1/n^2 - 1/m^2) where m and n are the principal quantum numbers of the two levels involved (for H-alpha, m=3,n=2; for H-beta, m=4...) and 911.75 is the vacuum wavelength of the Lyman limit (13.6 eV). The only missing piece is that these are vacuum wavelengths, needing modification for the index of refraction of air (multiply by 1/index). The table gives air wavelengths (I tnik that was for standard temperature and pressure). Bill Keel |
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