Why does cutoff voltage in photoelectric graph remain same regardless of change of intensity and frequency of light I understand in intensity that minimum voltage required to kick off slowest electron is constant as intensity is not related to energy of phtoelectron but cannot understand in case of frequency. I have attached a picture of the graphs:
Cut-off voltage in the photoelectric effect is a characteristic of the material and is in no way dependent on the intensity or frequency of light shown on the material. Why? Because cutoff voltage represents the amount of energy needed to knock-off the electrons from an atom and why would that change if you change the frequency or intensity of the incident light. I hope this helps.