Chapter 40469P40.18The energy needed isE==×−1 001 60 1019..eVJ.The energy absorbed in time interval ∆tisEtIAtP∆∆so∆tEIA×⋅×LNMOQP=×=−−160 10282 10128 10148191527...J500 J s mms days2ejejπ.The gross failure of the classical theory of the photoelectric effect contrasts with the success ofquantum mechanics.P40.19Ultraviolet photons will be absorbed to knock electrons out of the sphere with maximum kineticenergy Khfmax=−φ,orKmax.=×⋅×××FHGIKJ−=−−−6626 10300 10200 1010010470151348919JsmsmeV1.60JeVeVej.The sphere is left with positive charge and so with positive potential relative to V=0 at r=∞. As itspotential approaches 1.51 V, no further electrons will be able to escape, but will fall back onto thesphere. Its charge is then given byVkQre=orQrVke×⋅−−500 10899 10841 102912..m NmCNm CC22bg.P40.20(a)By having the photon source move toward the metal, the incident photons are Doppler
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