According to Moseley's law, the frequency ( $v)$ of the $K_\alpha$ line and the atomic number $Z$ of the element have the relation $(A$ and $B$ are constants)

• A

  $\frac{v}{(Z-A)}=B$
• Correct answer
  B

  $\frac{\sqrt{v}}{(Z-A)}=B$
• C

  $v(Z-A)=B$
• D

  $v(Z-A)^2=B$

Hence, the correct answer is option: 'B'.