The wavelength of `k_(alpha) ` X- rays produced by an X - rays tube is `0.76 Å` . The atomic number of the anode material of the tube is …….

Options

A. `20`
B. `60`
C. `40`
D. `80`

Answer

C

Explanation

The wavelength of `X` - ray lines is given by `Rydberg`
Formula `(1)/(lambda) = RZ^(2) ((1)/(n_(1)^(2)) - (1)/(n_(2)^(2)))`
For `K_(a)` "line" , `n_(1) = 1` and `n_(2) = 2`
`:. [ (4)/(3 (1.097 xx 10^(7) m^(-1)) (0.76 xx 10^(-10) m))]^(1//2) = 39.99 ~~ 40`