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When discovering the photoelectric effect, why did short wavelengths (high frequencies) eject electrons but long wavelengths (low frequencies) couldn't? Also, why did the intensity of the light not matter?
Light is made up of photons and the photon’s energy is dependent on its wavelength; longer wavelengths of light have less energy than shorter wavelengths, which is why the shorter wavelengths are able to eject the electrons (since they have more energy and you need to reach a certain threshold to eject the electron). The intensity doesn’t matter because it has to do with the frequency of the light.
A photon must have a wavelength that is lower than the threshold wavelength to have the required energy to eject electrons. According to the equation E = hv = hc/λ (λ being wavelength), having a long wavelength would decrease the energy needed to eject the electrons. Thus, having a shorter wavelength would produce the energy required to eject electrons.
Shorter wavelengths have higher frequencies, which means more energy to eject electron.. which is why the electrons are reactive to short wavelengths. And, the wavelength is not effected by the intensity of the light source, so there will not be more energy in the photons.
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