A cobalt (atomic no. =27 ) target is bombereded with electrons and the wavelength of its characteristic `x`-rays spectrum are measured. A seconf weak characteristic spectrum is also found due to an impurity in the target. The wavelength of the `K_(alpha)` lines `225.0pm` (cobalt ) and `100.0pm` (impurity). Atomic number of the impurity is `(take b=1)`

Options

A. `39`
B. `40`
C. `59`
D. `60`

Answer

B

Explanation

Using Mosely's law For for Both cobalt and impurity
` sqrtv=K(Z-1) Rightarrowsqrt(c/lambda)=K(Z-1)
sqrt(c/lambda_(c0))=K(Z_(co)-1)and sqrt(c/lambda)_(xx)=K(Z_(xx)-1)`
` sqrt(lambda_(c0)/(lambda_(xx)))=Z_(xx-1)/(Z_(c0)-1)RightarrowZ_(xx)=40`