12.The graph in Figure shows the kinetic energy of the most energetic photoelectrons as a function of the frequency of light falling on the cathode in a photoelectric cell. (a) According to the graph, what potential difference would be required to stop all the emitted electrons if the incident light had a frequency of 7.5 3 1014 Hz? (b) What is the physical significance of the intercept of the graph with the frequency axis (xaxis)? (c) What is the physical significance of the intercept obtained when the graph is extrapolated back to the kinetic energy axis (yaxis)? (d) Use the graph to determine a value for Planck's constant. Kinelic Energy (eV) 0 Frequency (x 10'\" Hz) 1 2 3 4 5 6 7 B 9 10