JEE Main & Advanced AIEEE Solved Paper-2004

  • question_answer
    The work function of a substance is\[4.0\text{ }eV\]. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

    A) 540 nm    

    B)                        400 nm

    C)        310nm                 

    D)        220 nm

    Correct Answer: C

    Solution :

    The work function is given by\[\frac{hc}{{{\lambda }_{0}}}=\phi \] where,\[{{\lambda }_{0}}\]is the threshold wavelength, \[\Rightarrow \]               \[{{\lambda }_{0}}=\frac{hc}{\phi }=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{4\times 1.6\times {{10}^{-19}}}\]                                 \[(\because 1\,EV=1.6\times {{10}^{-19}}J)\] \[=310nm\]


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