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466b - — — The answer is The photoelectric effect...

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Unformatted text preview: —+— The answer is @ The photoelectric effect occurs when light of sufficient frequency causes a metallic surface to emit electrons. The maximum kinetic energy of the electrons emitted equals the photon energy absorbed {E =frf } minus the work function, e. the energy required to enable the electron to escape the metal. Km = maximum kinelic energy ofan emitted electron _ hf _ [I] h = Planck's omstantfbjl I III“! - s} K111 _ f = frequency Iii‘l = work function {energy required toescape lhe metal} Current ceases when the energy required to move an electh from the positive to the negative plate [evil]: exceeds the maximum kinetic energy of emitted electrons. They don't have enough energy to go against the voltage and make it across the gap. The particular ‘vfl required to stop the current increases directly with photon frequency because this directly reflects the electron kinetic energy left over after escape. Notice also that for low frequencies, the current is zero even with zero v“ because, in that range, the photon energy is not great enough to overcome the work function and produce photoelectrons. THE PlE‘I" EMEPTUAL STEP FDR MEET PHDTDELECTRIC EFFECT PRDELEMS IS TO APPL‘I' THE EMAN— TIZATEDH OF LIGHT EHERETAS PHDTGHS [E : hf I. © £26135 .J WHEEL ...
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