A particle of mass $m$ and charge $q$ is accelerated through a distance $d_1$ by an electric field $\vec{E}$. Another particle of mass $M$ and charge $q$ is accelerated by the same electric field through a distance $d_2$. Both the particles emerge with the same de Broglie wavelength $\lambda_B$. What is the ratio of the distances $d_2 / d_1$ ?

Two monochromatic sources emit light at wavelengths $\lambda$ and $\lambda / 2$. The stopping potentials for a photosensitive material using these two sources are found to be 1 V and 3 V , respectively. What is the work function of the material?