NEET Sample Paper NEET Sample Test Paper-38

  • question_answer
    When photons of energy hv fall on an aluminium plate (of work function\[{{E}_{0}}\]), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be

    A) \[K+{{E}_{0}}\]

    B)  2K

    C)  K

    D)  \[K+hv\]

    Correct Answer: D

    Solution :

     According to Einstein's photoelectric effect energy of photon = KE of photoelectron + word function of metal That is, \[hv=\frac{1}{2}m{{v}^{2}}+{{E}_{0}}\] \[hv=\frac{1}{2}m{{v}^{2}}+{{E}_{0}}\] or \[hv={{K}_{\max }}+{{E}_{0}}\] Now, we have given, \[v'=2v\] Therefore, \[K_{\max }^{'}=2hv-{{E}_{0}}\] From Eqs. (i) and (ii), we have \[K_{\max }^{'}=2({{K}_{\max }}+{{E}_{0}})-{{E}_{0}}\] \[=2{{K}_{\max }}+{{E}_{0}}={{K}_{\max }}+({{K}_{\max }}+{{E}_{0}})\] \[={{K}_{\max }}+hv\] [From Eq. (i)] Putting \[{{K}_{\max }}=K\Rightarrow K_{\max }^{'}=K+hv\]


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