JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Self Evaluation Test - Dual Nature of Radiation and Matter

  • question_answer
    Radiation of wavelength \[\lambda \], is incident on a photocell. The fastest emitted electron has speed v. If the wavelength is changed to \[\frac{3\lambda }{4}\], the speed of the fastest emitted electron will be:

    A) \[=v{{\left( \frac{4}{3} \right)}^{\frac{1}{2}}}\]

    B) \[=v{{\left( \frac{3}{4} \right)}^{\frac{1}{2}}}\]

    C) \[>v{{\left( \frac{4}{3} \right)}^{\frac{1}{2}}}\]

    D) \[<v{{\left( \frac{4}{3} \right)}^{\frac{1}{2}}}\]

    Correct Answer: C

    Solution :

    [c] \[hv_{0}^{2}-h{{v}_{0}}=\frac{1}{2}m{{v}^{2}}\] \[\therefore \frac{4}{3}h{{v}_{0}}-h{{v}_{0}}=\frac{1}{2}mv{{'}^{2}}\]  \[\therefore \frac{v{{'}^{2}}}{{{v}^{2}}}=\frac{\frac{4}{3}v-{{v}_{0}}}{v-{{v}_{0}}}\text{          }\therefore v'=v\sqrt{\frac{\frac{4}{3}v-{{v}_{0}}}{v-{{v}_{0}}}\text{ }}\] \[\therefore \,\,\,v'>V\sqrt{\frac{4}{3}}\]


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