The Kα X-rays of aluminum (Z = 13) and zinc (Z = 30) have wavelengths 887 pm and 146 pm respectively. Use Moseley’s law √v = α (Z – b) to find the wavelength of the Kα X-ray of iron (Z = 26).

Given:


Kα X-rays of zinc and aluminum have wavelengths, respectively




By using the formula



frequencies of Kα X-rays of zinc and aluminum, respectively are




Using Moseley’s law √v = α (Z – b),


for Aluminum,



for Zinc,



Dividing equations 1 by 2,



solving. we get


b=


Therefore


a =


for Fe(Iron), Frequency is given by




By using the formula



wavelength of Kα X-rays given out by Iron atom is given by



1