JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Critical Thinking

  • question_answer
    A silver ball of radius 4.8 cm is suspended by a thread in the vacuum chamber. UV light of wavelength 200 nm is incident on the ball for some times during which a total energy of 1 ´ 10?7 J falls on the surface. Assuming on an average one out of 103 photons incident is able to eject electron. The potential on sphere will be

    A)            1 V

    B)            2 V

    C)            3 V

    D)            Zero

    Correct Answer: C

    Solution :

                       \[n=\frac{E\lambda }{hc}\]\[=\frac{1\times {{10}^{-7}}\times 200\times {{10}^{-9}}}{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}=1\times {{10}^{11}}\]            Number of electrons ejected \[=\frac{{{10}^{11}}}{{{10}^{3}}}={{10}^{8}}\]            \ \[V=\frac{q}{4\pi {{\varepsilon }_{0}}r}=\frac{({{10}^{8}}\times 1.6\times {{10}^{-19}})\times 9\times {{10}^{9}}}{4.8\times {{10}^{-2}}}=3\,V\]


You need to login to perform this action.
You will be redirected in 3 sec spinner