The adjoining figure represents the observed intensity of X-rays emitted by two different tubes A and B as a function of wavelength  $\lambda$. For the tube A, the potential difference  between the filament and target is  ${\text{V}}_A$  and atomic number of target is $Z_A$  For the tube B,  corresponding potential difference is ${\text{V}}_B$  and the atomic number is ${\text{Z}}_B$ . The solid curve is for  tube A and dotted curve for tube B; then :