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a.Every metal has a definite work function. Why all photoelectronsdo not come out with the same energy of incident radiation in monochromatie ? Why there is an energy distribution of photoelectrons? b. The energyand momentumof an electron are related to the frequency and wave-length of the associated matter wave by the relations, E=h upsilon, p=(h)/(lambda) But while the value of lambda is physically significant, the value of upsilon (and therefore the value of the phase speed upsilon lambdahas no physical significance. Why? |
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Answer» Solution :a. Work functionis MINIMUM amount of energy required for the electron in the topmost level of the CONDUCTION band to get out of the metal. All the electrons do not belong to this topmost level. Different electrons are knocked off from the metal from different levels, with different energyfor the same incident radiation. Thus the emitted electrons occupy a continuous band of ENERGYLEVELS. B. The absolute VALUE of energyE (but not momentum, p) of any particle is arbitraryto within an additive constant. Hence absolute value of `.upsilon.` of a metter wave has no direct physical meaning, while `.lambda.` is physically significant. The phase speed `(upsilon lambda)`is physically insignificant, while group speed is physicallysignificant. |
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