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

  • question_answer
    When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. 'The work function of the metal is                                         [NEET 2014]

    A)   0.65 eV

    B)                  1.0 eV

    C)  1.3 eV 

    D)       1.5 eV

    Correct Answer: B

    Solution :

    For photo electric equation
    \[{{(KE)}_{\max }}=hv-{{\phi }_{0}}\]
    For the first condition
    \[0.5=E-{{\phi }_{0}}\]              …(i)
    For the second condition
    \[0.8-1.2E-{{\phi }_{0}}\]                       …(ii)
    From Eqs. (i) and (ii)
    \[0.5=E-{{\phi }_{0}}\]
    and      \[0.8=1.2E-{{\phi }_{0}}\]
                \[-0.3=-0.2E\]
    \[E=\frac{0.3}{0.2}1.5eV\]
    From expression (i)
                \[0.5=1.5-{{\phi }_{0}}\Rightarrow {{\phi }_{0}}=0.5-0.5=1eV\]


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