JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Photon and Photoelectric Effect

  • question_answer
    Assuming photoemission to take place, the factor by which the maximum velocity of the emitted photoelectrons changes when the wavelength of the incident radiation is increased four times, is                            [Haryana CEE 1996]

    A)            4    

    B)            \[\frac{1}{4}\]

    C)            2    

    D)            \[\frac{1}{2}\]

    Correct Answer: D

    Solution :

                       \[\frac{hc}{\lambda }={{W}_{0}}+\frac{1}{2}mv_{\max }^{2}\] Assuming \[{{W}_{0}}\] to be negligible in comparison to \[\frac{hv}{\lambda }\] i.e. \[v_{\max }^{2}\propto \frac{1}{\lambda }\Rightarrow {{v}_{\max }}\propto \frac{1}{\sqrt{\lambda }}\]. (On increasing wavelength l to 4l, vmax becomes half).


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