In the photoelectric effect, what happens as you increase the frequency of light keeping the same intensity constant?
E=hf, so as you increase the frequency of light, the energy of each photon hitting the metal surface is greater. Thus the electrons liberated from the surface of the metal have a greater maximum kinetic energy.
We also said that the intensity of the light should stay the same. Intensity = Power/Area = (Energy/time)/Area. Given that the energy of each photon is greater with a higher frequency of light, there must be fewer photons hitting the metal surface per unit time in order to keep the intensity constant.
Thus, assuming that initially the photon frequency was above the threshold frequency, increasing the frequency at the same intensity will increase the kinetic energy of the photoelectrons liberated from the metal surface, but also reduce the number of electrons released.
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