The Kα X- rays arising from a cobalt (Z=27) target have a wavelength of 179 pm. The Kα X rays arising from a nickle target (Z=28) is
> 179 pm
< 179 pm
= 179 pm
None of these
λ∝1(Z−1)2
λNiλCo=(ZCo−1ZNi−1)2=(27−128−1)2 λNi=(26)2(27)2λCo (λNi<λCo)