The `K_(alpha)` `X` - rays arising from a cobalt `(z = 27)` target have a wavelength of `179 pm`. The `K_(alpha)` `X` - rays arising from a nickel target `(z = 28)` is

Options

A. `gt 179 pm`
B. `lt 179 pm`
C. `= 179 pm`
D. None of these

Answer

B

Explanation

`lambda_(k_(a)) prop (1)/((Z - 1)^(2)) rArr (lambda_(Ni))/(lambda_(Co)) = ((Z_(Co) - 1)/(Z_(Ni) - 1))^(2) = (( 27 - 1)/(28 - 1))^(2)`
`l_(Ni) = ((26)/(27))^(2) xx lambda_(Co) = ((26)/(27))^(2) xx 179`
`= 165.9 pm lt 179 pm`.