If the frequency of `k_(alpha)` x-ray emitted from the element with atomic number 31 is f, if the frequency of `k_(alpha)` x-ray emitted from the element with atomic number 51 , is given by `25/x f` then x is (assume that screening constant for `K_(alpha)` is 1)

Explanation

`sqrt(f) a=(Z-1)`
`sqrt(f) a(31-1)`
`sqrt((25f)/x) =a(51-1)`
x=9