S1 : When ultraviolet light is incident on a photocell, its stopping potential is $V_{\circ}$ and the maximum kinetic energy of the photoelectrons is $K_{max}$ increase. . When the ultraviolet light is replaced by x-rays, both $V_{\circ}$ and $ K_{max}$ S2 : Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.