The frequencies are related to atomic number by the equation: $\sqrt{\nu }=\text{a}(\text{Z}-\text{b})$

Z is Nuclear charge or atomic number                          

$\text{'}\nu \text{'}$  is Frequency

Plot between $\sqrt{\nu }$ and Atomic mass is a Zig Zag curve

Plot between$\sqrt{\nu }$  And atomic number is straight line.

This experiment was conducted by Moseley.