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An increase in intensity only leads to an increase in the number of electrons that are ejected, not an increase in the kinetic energy of the electrons. This is the photoelectric effect. An increase in the kinetic energy would occur with an increase in intensity if light behaved like a wave in the wave model.
Increasing the light intensity only increases the number of photons. To remove electrons, we need the energy of the photon to be greater than or equal to the energy needed to remove an electron. If you have this energy, then increasing the light intensity results in more ejected electrons. Light does not act like a classical wave (intense/bigger wave has more energy) as light sources with long wavelengths (low frequency) light cannot eject electrons even with high intensity light. However, light sources with short wavelengths (high frequency) can eject electrons because energy is inversely proportional to wavelength.
If you look at the equation E=hv, you can see that only the frequency and not wavelength/intensity affects E. Therefore, increasing the intensity does not increase the kinetic energy of the electrons
Increasing intensity means you increase the NUMBER of photons (not the energy each particular photon carries), and to emit e- from metal surface, you need EACH photon to carry a certain amount of energy (threshold energy). In order to do that, you must increase the frequency of the light source
Since light doesn't behave like a classical wave that is (bigger wave=more intensity). The only way to obtain an emitted electron is to have the energy of a photon be greater than the energy needed to remove an electron. Light sources (short wavelength=high frequency) can eject e- even with low intensity light which is different from the classical wave which follows the idea that wave properties result in ejected electrons when intensity is increased.
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