A photosensitive material would emit electrons if it is excited by a photon beyond a threshold. To cross the threshold, what should be increased?

Explanation

Einstein's Photoelectric Effect equation is: hf = hfo + KEmax Where hf is the energy of the photon, hfo is the work function of the material, and KEmax is the surplus energy that enables the electron to leave the surface of the material. The work function (hfo) is the minimum or threshold energy required to cause the photoelectric effect. If the energy of a photon is less than hfo, not enough energy would be transmitted to the electron to come up to the surface, and there would be no photoelectric effect. Thus by increasing the frequency and decreasing the wavelength, the threshold for the photoelectric effect can be crossed. The intensity of light does not affect the threshold. It only affects the number of electrons emitted and hence, the photocurrent. The voltage of the source affects current; increasing the positive voltage (when the cathode is negative) increases the current while increasing the negative voltage (when the cathode is positive) decreases the current. At a particular value of negative voltage, called the stopping potential, the current becomes zero.