NEET Physics Atomic Physics NEET PYQ-Atomic Physics

  • question_answer
    The work function of a surface of a photosensitive material is 6.2 eV. The wavelength, of the incident radiation for which the stopping potential is 5 V lies in the                                                               [AIPMPT (S) 2008]

    A)  ultraviolet region

    B)       visible region

    C)  infrared region  

    D)       X-ray region

    Correct Answer: A

    Solution :

    According to laws of photoelectric effect \[K{{E}_{\max }}=E-\phi \] where \[\phi \] is work function and \[K{{E}_{\max }}\] maximum kinetic energy of photoelectron.
    \[\therefore \]      \[hv=e{{V}_{0}}+\phi \]
    or         \[hv=5\,eV+6.2\,eV=11.2\,eV\]
    \[\therefore \]      \[\lambda =\left( \frac{12400}{11.2} \right){\AA}\approx 1000{\AA}\]
    Hence, the radiation lies in ultraviolet region.


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