# In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be $4.12 \times 10^{-15}Vs$. Calculate the value of Planck’s constant.
$\begin {array} {1 1} (a)\;6.592 \times 10^{-34} Js & \quad (b)\;6.626 \times 10^{-34} Js \\ (c)\;659.2 \times 10^{-35} Js & \quad (d)\;66.26 \times 10^{-35} Js \end {array}$