Figure $2\mathrm{.}47$ of Elliott shows four sharp peaks superimposed on broad spectrum for $40kV.$ Justify their relative wavelengths based on their origin. In the same figure, the starting wavelength of curves moves to the right with decreasing value of anode potential. Explain, why?

Fig$\mathrm{.}2\mathrm{.}47$ Intensity of $x-$rays emitted from an $Ag$ target versus wavelength for the values of anode potential marked. At sufficiently high electron acceleration voltages, sharp peaks due to X$-$ray emission from intra$-$atomic electronic transitions are superimposed on the broad bremsstrahlung background. $($After Burns $(1985).$ Reproduced by permission of Academic Press, Inc.$)$