RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    The work function for aluminium surface is 4.2eV. The cutoff wavelength for photoelectric effect is:

    A)  \[1000\,\overset{\text{o}}{\mathop{\text{A}}}\,\]                        

    B)  \[2000\,\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C)  \[2955\,\overset{\text{o}}{\mathop{\text{A}}}\,\]        

    D)         \[4200\,\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: C

    Solution :

    Using the relation \[W=\frac{hc}{\lambda }\,so,\lambda =\frac{hc}{W}\] or            \[\lambda =\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{4.2\times 1.6\times {{10}^{-19}}}\]                       \[2955\,\overset{\text{o}}{\mathop{\text{A}}}\,\]


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