NEET Physics Photo Electric Effect, X- Rays & Matter Waves NEET PYQ-Photo Electric Effect,X-Rays

  • question_answer
    Two radiations of photon energies 1 eV and 2.5 eV, successively illuminate a photosensitive metallic surface of work function 0.5 eV. The ratio of the maximum speeds of the emitted electrons is                                  [AIPMT (M) 2012]

    A)  1 : 4    

    B)       1 : 2    

    C)  1 : 1    

    D)              1 : 5

    Correct Answer: B

    Solution :

    We have \[\frac{1}{2}m{{v}^{2}}_{\max }=E-\phi \]
    Here case (i)      
    \[\frac{1}{2}m{{v}^{2}}_{1\,\max }=(1-0.5)eV\]
    \[\frac{1}{2}mv{{_{2}^{2}}_{\,\max }}=(2.5-0.5)eV\]
    Hence,  \[\frac{v_{1}^{2}\max }{v_{2}^{2}\max }=\frac{1}{4}\]
    \[\frac{{{v}_{1\max }}}{{{v}_{1\max }}}=\frac{1}{2}\]


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