1. The problem statement, all variables and given/known data Determine Planck's Constant from gradient 2. Relevant equations 3. The attempt at a solution I have a graph entitled "Photoelectric effect: stopping voltage as a function of light frequency" The y-axis is the Stopping Voltage (V), the x-axis the Frequency (Hz). How do I determine Planck's Constant (h) from the gradient? Thanks!