Introduction|| Revision OF 9th class construction || Some important topic discussion used in construction || Division OF line Segment in given ratio by two different method

Introduction || Revision OF 9th class || Surface area and volume || Formula discussion

Division of a life segment in a given ratio |Construction of tangent to a circle

Introduction || Revision OF 9th class Statistics || Simplified methods to calculate Mean || Direct method || Assumed mean method || Step-division method

Excited atoms emit radiations consisting of only certain discrete frequencise or wavelengths. In spectroscopy it is often more convenient to use freuquencies and wave numbers are proportional ot energy and spectroscopy involves transitions between different energy levels . The line spectrum shown by a single electron excited atom (a finger print of an atom) can be given as 1/(lambda)=barvR_(H).Z^(2)[(1)/(n_(1)^(2))-(1)/(n_(2)^(2))] where Z is atomic number of single electron atom and n_(1),n_(2) are integers and if n_(2)gt n_(1), then emission spectrum is noticed and if n_(2)ltn_(1), then absorption spectrum is noticed. Every line in spectrum can be represented as a difference of two terms (R_(H)Z^(2))/(n_(1)^(2)) "and"(R_(H)Z^(2))/(n_(2)^(2)). The ratio of wavelength for II line fo Balmer series and I line of Lyman series for H-like species is :