BCECE Medical BCECE Medical Solved Papers-2010

  • question_answer
    Light of two different frequencies whose photons have energies 1 eV and 2.5 eV successively illuminate a metal of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons will be

    A)  1 : 5           

    B)  1 : 4

    C)  1 : 2           

    D)  1 : 1

    Correct Answer: C

    Solution :

    According to Einsteins photoelectric equation,                 \[({{E}_{K}})=hv-{{\phi }_{0}}\]                 \[({{E}_{K}})=1-0.5=0.5\,eV\] Similarly, \[{{({{E}_{K}})}_{2}}=2.5-0.5=2eV\] \[\therefore \] \[\frac{{{({{E}_{K}})}_{1}}}{{{({{E}_{K}})}_{2}}}=\frac{1}{4}\] \[\Rightarrow \] \[\frac{\frac{1}{2}mv_{1}^{2}}{\frac{1}{2}mv_{2}^{2}}=\frac{1}{4}\] \[\Rightarrow \] \[\frac{v_{1}^{2}}{v_{2}^{2}}=\frac{1}{4}\] \[\Rightarrow \] \[\frac{{{v}_{1}}}{{{v}_{2}}}=\frac{1}{2}\]


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