JEE Main & Advanced Sample Paper JEE Main Sample Paper-19

  • question_answer 50) Lights of two different frequencies, whose photons have energies \[1\text{ }eV\] and \[2.5\text{ }eV\] respectively successively illuminate a metal whose work function is \[0.5\text{ }eV\] 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 :

     Einstein equation KE   = E - Work function; \[\frac{1}{2}m{{v}^{2}}=E-W\] Using this concept, \[\frac{\frac{1}{2}mV_{1}^{2}\max }{\frac{1}{2}V_{2}^{2}\max }=\frac{1-.5}{2.5-.5}=\frac{1}{4}\] or \[\frac{{{V}_{1}}\max }{{{V}_{2}}\max }=\frac{1}{2}\]

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