The square root of frequency of a spectral line is directly proportional to the atomic number √v∝Z √v=a(Z−b) a and b are constants they do not depend upon the nature of the target material.b depends upon the series. b=1 for K - series and 7.4 for L - series. a depends upon the line of the series. It is given by the slope of the graph between √v and Z. b is given by the X - intercept of the graph between √v and Z. Hence right answer is A : 3, C: 2, B : 2,3,4 , D: 4