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. 30
B. 40
C. 50
D. 60

Answer

B

Explanation

`(1)/(lambda) = Z^(2) R_(oo) ((1)/(n_(1)^(2)) - (1)/(n_(2)^(2)))`
for `K_(alpha) line , n_(1) = 1 and n_(2) = 2`
`(1)/(lambda) = Z^(2) R_(oo) (3)/(4)`
`Z = sqrt((4)/(3lambda R_(oo))) = 39.9 = 40`