The work function of potassium is 2.0 eV. When it is illuminated by light of wavelength 3300 Å photo electrons are emitted. The stopping potential of photo electrons is (in volts) [Plank's constant  $\text{h}=6.6\times {10}^{-34}\text{\hspace{0.17em}Js},1\text{\hspace{0.17em}eV}=1.6\times {10}^{-19}\text{J,\hspace{0.17em}C}=3\times {10}^8{\text{\hspace{0.17em}ms}}^{-1}]$(Round off to the nearest integer)