KVPY SA Exam 2012 Question Paper

A plot of the kinetic energy $(1/2\mv^2)$ of ejected electrons as a function of the frequency (v) of incident radiation for four alkali metals $(M_1, M_ 2, M_ 3, M _4)$ is shown below. The alkali metals $M_1, M_ 2, M_ 3$, and $M _4$ are, respectively