Question

Frequencies of $K_{\alpha }$ X-rays of different materials are measured. Which one of the graphs in figure may represent the relation between the frequency f and the atomic numbe Z.

• A. d
• B. c
• C. b
• D. a

Answer 1

The correct option is A d

According to Moseley's law, frequency $\nu \propto (Z-b{)}^2$

For $K_{\alpha }$ line, the screening constant $b=1$ so $\nu \propto (Z-1{)}^2$

This is an equation of parabola like $y=a{x}^2+bx+c$ and thus curve d is that parabola.