The potential difference between the cathode and the target electrode in a Coolidge tube is changed from $20\mathrm{kV}$ to $30\mathrm{kV}$. By what percent the minimum wavelength of the emitted X-rays will change? 

The $\frac{e}{m}$ of electron is $1.76\times {10}^{11}{\mathrm{ckg}}^{-1}$ and stopping potential is $0.71 \mathrm{V}$, then the maximum velocity of the photoelectrons is :

This question has statement-$1$ and statement $-2$ of the four choices given after the statements, choose the one that best describes the two statements. A metallic surface is irradiated by a monochromatic light of frequency $v>v_0$ (the threshold frequency). The maximum kinetic energy and stopping potential are ${\mathrm{K}}_{\max }$ and ${\mathrm{V}}_0$ respectively. If the frequency incident on the surface is doubled, both the ${\mathrm{K}}_{max}$ and ${\mathrm{V}}_0$ are doubled.

Statement-II The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light: