BITSAT 2012 Paper

Energy of incident radiation is given by:
E=‌

hc

λ

=‌

6.64*10−34*3*108

300*10−9

=6.64*10−19=4.05eV
The work function of the metal is equal to 2.54eV Hence the maximum kinetic energy of an ejected photoelectron would be 1.59eV And the stopping potential needed to stop this would be 1.59V.